Not to mention how weakened infernape is by weather in all of it's forms. In sand or hail it dies to fast, and in rain it's fire type moves are weakened. It has u-turn but nothing to distinguish it from other high speed users of the move.
I would say that the best wall breaker of this generation is SD rock gem terrakion, if it gets a sub up then the opponent has no way of predicting around it, extremely threatening. Following that I would say that CB scizor is actually very dangerous to stall teams because of Pursuit, in conjunction with Choice Specs Rotom-W and Terrakion you have a virtually unstoppable offensive core, but even by itself CB scizor is extremely useful against stall teams.
What distinguishes a good wallbreaker from an okay one is that the best ones are good against both stall and offense. Think of Lucario, Terrakion, and SD Scizor, they have a lot of utility in addition to their power.
EDIT:
Here are my nominations for tier one wall breakers:
SD Lucario: The gold standard of set-up sweepers, Lucario retains it's status as the number one most threatening pokemon this generation, just like it was in DPPt. It can run 2 different priority moves and other than Slowbro, nothing likes coming in on repeated Close Combats. Gliscor may seem to shut it down entirely, but Lucario can always choose to run various coverage moves to wreck whatever wall is currently fashionable to use against it.
Scizor SD and CB: SD Scizor is not quite as dangerous to stall as Lucario, but it is significantly more powerful and LO Bullet Punch can clean up offensive teams late game even without Swords Dance. The CB version is just unbelievably good, it traps things, revenges things, abuses entry hazards... In my opinion it is significantly more threatening in BW than it ever was in DPPt despite being unchanged.
In my mind both of these pokemon are vastly superior to LOL Hydreigon, LOL Infernape, and LOL Tyranitar (it isn't a even a wall breaker it's maybe a lure, maybe).
Just a reminder that this topic is looking solely at a Pokemon's performance against WALLS. While it's nice to have a wallbreaker that can double as a sweeper and a stallbreaker that can double as a wall,
that does not necessarily make them tier 1 material. The teirs are
solely based on wallbreaking/stallbreaking ability.
Still, I'll add your nominations as I know Lucario in particular can be horrifying to stall. Scizor on the other hand can't break through really any dedicated physical walls. Skarmory, Hippowodon, Vaporeon, Jellicent, and others all beat SD scizor 1 on 1. Definitely not Tier 1 material in my opinion, though it obviously has a lot of other merits in other areas.
And another reminder
Being hard walled by ONE or TWO Pokemon does not disqualify a Pokemon from being Tier 1. It needs to be able to beat the vast majority of walls overall, and have the capability to defeat at least say, 70% of walls with one moveset. Not everything can be Salamence you know; not even Terrakion or Dragonite can boast the ability to take out all but of the walls in the game with only one moveset. If we had that requirement, Salamence would be the only one in the tier!
However I am on the fence with Infernape myself. It does beat the vast majority of walls, but there are a sparse few like Latias and Jellicent that consistently give it trouble. However, it should be noted that it can potentially 2HKO Latios with a choice band set after rocks with Stone Edge, and will 2HKO Jellicent with grass knot after a NP boost, so it technically can get past them. It just isn't likely to do it with a classic mixed set. Still it does fit the definition of Tier 1, as I dare you to come up with another Pokemon that walls it. Two Pokemon isn't enough to discredit it as top tier wallbreaker, given the fact that it's pretty incredible that it's walled by so few in the first place.
As for some of the other nomineesL
I don't think Alakazam really counts because it isn't strong enough to muscle past Blissey (let alone Chansey) with a Life Orb set and the Choice set relies on way too many moves that have major Pokemon immune to them (Psychic walled by Tyranitar, Focus Blast by any Ghost type, Shadow Ball by any normal type, HP Fire by Heatran and Bulky waters, Energy ball by anything not a bulky water with a decent SpD stat), making it unsuitable for wallbreaking. I know my answer to Alakazam is always to switch in a special wall, and that itself is a testament to the fact that it's not really a wall breaker.
Tyranitar... I never really understood the reasoning for it as a wallbreaker in the first place. The CB set isn't going to be breaking through really any physically defensive mons, It's too slow to 2HKO Gliscor with Stone Edge and a plethora of lesser used mons completely wall it, though Skarmory can potentially be 2HKO'd by Stone Edge... but then you just switch to something that resists Stone Edge. The mixed sets suffer horribly from low speed and 4MSS, and Jellicent shuts it down completely with will-o-wisp. The bottom line is although it can run a set to KO virtually any defensive Pokemon, it has no one set that beats enough of them to be Tier 1.
I have my doubts with Haxorus' reliability as a wall breaker due to its fragility, but after looking at the calcs I see only Ferrothorn, Skarmory and Metagross with Air Balloon being able to wall the CB set, and if the sets with SD set up... well you can say goodbye to at least 2 Pokemon if you can't revenge kill it. Of course, that very revenge killing is it's biggest problem; thanks to its fragility, it can usually only take out one wall per a game before being KO'd, which isn't enough for Tier one. However against teams without faster Pokemon and Priority it CAN do it... but that's an awfully specific condition.
I only suggested Latios because I thought it close enough to deserve a vote too; I personally don't believe it's tier 1 material. Again, it is capable of breaking through all the walls around (even ttar is 2HKO'd by Modest choice specs surf with SR), but can only do so in specific conditions, and usually not all in one set. Without Psyschock the blobs wall it, it needs weather to muscle past Sdef Jirachi, Tyrantitar beats most sets too. Tier 2 at least for sure but Tier 1? It's cutting it pretty close.
