Entei languishes in the far depths of Limbo beside Pokemon such as Luvdisc, Unown and Corsola. Contrary to where Entei resides in these temporary tiers, it has shown itself to be able to hold its own in battle. Take into consideration Entei's usage statistics. What I would like to point out in this is Entei's weight. An average weight is around .5 where as Thundurus-Incarnate has .74, being used almost exclusively by high ranking players and winning a majority of battles it is in. A weight for a "good" Pokemon is .64, which by all means qualifies Entei as not the horrible, shit Pokemon people claim it to be. Truly, no other Pokemon can affect a battle in quite the same way as Entei can, offensively spreading burns with its powerful Sacred Fire without having to lose momentum nor predict a switch with Will-o-Wisp while also taking repeated hits and shrugging them off. Nothing short of a Heatran can consistently switch in safely, either taking a powerful hit with a very high chance of burn or one of Entei's coverage moves, either way setting it up to be just as likely hit by a powerful Extremespeed as it is to force Entei out. Even Flash Fire Chandelure, being immune to both attacks, is of no avail since Entei can hit it with an instantly lethal Stone Edge. An Adamant Entei (required Nature for any Entei with the event move Extremespeed) has 2 more Atk than a timid Latios has SpAtk. In addition to this, Entei has the highest base HP of any Fire type to date. These factors would allow us to build a core where Entei's role is very much a central aspect of the core, preventing it from effectively being replaced with another similar Pokemon, such as Mega Charizard-X. Regarding Builds: Entei is in a very precocious speed tier and, due to the nature required to have Extremespeed, can't have a beneficial nature. For this reason, I see Entei better suited by being built bulky rather than fast. For my own build, I use 172 HP/252 Atk/84 SpDef. This is enough to bring its SpDef up to par with its Def while bringing its Atk to a threatening 361, particularly powerful when combined with STAB Sacred Fire. For attacks, Entei really only has 5 moves. The standard Entei uses Sacred Fire, Stone Edge, Extremespeed and Iron Head/Bulldoze. The combination of Sacred Fire and Extremespeed is what gives Entei its punch, being able to hit for amazing STAB damage with a very high chance to cause a potentially crippling burn and then follow up with a high power and high priority move. Regarding Weaknesses: Entei is predictable. That is its greatest drawback, but something that can be mitigated with our new core. Aside from this, Entei has a weakness to Water, Ground and Rock, all common attacking types. Furthermore, this means Entei has a weakness to one entry hazard and cannot avoid any of them. Entei is truly resisted and threatened by very few things: Ground/Water Pokemon, Jellicent and virtually any Rock type (read: Terrakion). Despite this, very few Pokemon can truly counter Entei because not much of anything would want to switch in on it. Not even Guts Entei can switch in, getting off one hit at the very most. Notably Heatran, Mega Charizard X and Chandelure can switch in effectively and effectively threaten/decommission Entei. Heatran and Chandelure soak up a Sacred Fire with their Flash Fire while Megazard-X has a double resistance to it (just a resistance if it hasn't yet gone Mega) and an immunity to burns. Heatran and Megazard-X greatly threaten Entei with Earth Power and Earthquake. Chandelure, however, can effectively cripple Entei by Tricking Choice Specs onto it. At least one member of the core should be able to mitigate or compensate for these drawbacks. Regarding Items: I agree that Choice Band isn't the ideal item for Entei. In the set I have been testing, I chose to use Leftovers to compliment and strengthen Entei's bulk and increase its longevity. I could also see an Assault Vest giving Entei a great boost to bulkiness without hindrance due to its heavy reliance on attacks with minimal, if any, need for status moves. Life Orb can artificially boost Entei's damage, but at the cost of bulkiness. Expert Belt would be less than optimal for Entei as it relies very little on supereffective damage. A type boosting item, such as Charcoal or one of Arceus's plates, could provide an excellent power boost without sacrificing bulk. Weakness Policy is a good possibility, but in the event that something like Manaphy comes in, Entei would be better off switching out than trying to keep the +2 Atk. There's also a special niche for Sitrus Berry and berries that reduce super effective damage, providing Entei with a boost to bulkiness when most needed. In short, I think that the best items for Entei are Leftovers, Assault Vest and type boosting items (Charcoal and Silk Scarf especially). The former two are for bulk (in very different ways) while the last group of options help boost Entei's damage in certain situations without any sacrifice to bulk. Regarding Partners: Entei has many options to choose from. AriadosPerson already elaborated beautifully on the option of Zapdos, so I will focus now on Entei's other options. The first clear choice to pair Entei with would be a specially bulky Pokemon with low physical bulk. Entei's constant burning of everything does much to artificially increase this bulk, making them difficult to topple. A few Pokemon that come to mind would be Milotic, Chansey/Blissey, Goodra, Latias and Togekiss. Chansey, Blissey, Latias and Togekiss can all act as a cleric to heal off damage and status afflictions Entei may have taken, further expanding his reign of fire. Milotic, Goodra, Latias and Togekiss both resist something that would be powerful enough to threaten Entei out (Milotic and Goodra taking almost nothing from Surf while Togekiss finds itself immune to Earth Power. Latias stands out as having both qualities.) which would allow a clean switch. The only shared weakness comes in the form of Togekiss's Flying type taking super effective damage from Rock, of which only Hidden Power, Ancientpower and Power Gem are special. As far as offensive presence is concerned, Goodra, Latias and Togekiss can hit where Entei cannot, such as bulky Water types and virtually anything Rock type, such as Terrakion. Latias additionally finds itself able to make use of Defog to clear out any hazards that would threaten Entei. All of these Pokemon also find themselves adept at spreading status conditions while Entei is away, with all but Latias already filling that role in the current meta. Entei could also do well with an aggressive pivot that could switch in, take a hit and then threaten out the opponent while switching to the third member of the core. Latias, Slowbro, Manaphy and Rotom-Wash stand out as the best choices for this position. Rotom, however, is by far disqualified from being in this core because of its position of most used Pokemon in OU. That leaves us with Latias and Slowbro able to switch in and take repeated hits due to their recovery options (Latias with Recover/Roost and Slowbro with Slack Off and Regenerator). On the other hand, Manaphy has access to U-Turn is expected to spend its first turn in using Tail Glow, which would lead many opponents to switch to something that can take care of Manaphy, leading into a clean U-Turn to either Entei or the third core member. The final form of partner that here is the specially offensive, bulky Water type. This would best be complimented by having the third be an aggressive Grass type. The Pokemon I could see filling this role would be Rotom-Wash, Mega Blastoise, Clawitzer, Manaphy, Slowbro and Milotic. Manaphy is well known for its use of the astoundingly powerful Tail Glow for offensive presence and its 100/100/100 defenses. Milotic is able to hit for good damage with Scald while also finding itself in possession of Dragon Tail, letting it phase out opponents. Slowbro has a number of good options to work with, including Calm Mind, Regenerator and Scald. (Spoiler alert, they all have Scald.) Mega Blastoise and Clawitzer are essentially the same Pokemon. Mega Blastoise has slightly better everything, but Clawitzer has the ability to use items and does not take up a Mega slot. I think Goodra deserves a special mention here since it accomplishes pretty much everything this category sets out to do while also being resistant or even immune to Grass as well as resisting Electric attacks. The ideal Pokemon to pair Entei with for this, as far as I can see, would be Zapdos, Goodra, Latias, Slowbro, Manaphy and possibly Togekiss. Each one pairs well with Entei and covers some weaknesses without fully covering them all. The main uniting factor of these Pokemon it that they bring exceptional special bulk, decent special offense and resist something that threatens Entei, although none of them resist Rock and two of them even share that weakness. This gives us a good direction to go with regarding our CAP, but it also leaves enough room that each of these individual partners would have a different perfect fit for the third Pokemon of the core. TLDR: I put 5 hours of thought and hard work into this, please don't skip over it. What do you mean weaker attacking stat? Sacred Fire is physical, Entei has 25 more Atk than SpAtk and Entei has access to moves such as Extremespeed.