Hazardous Waste: Screw Toxic, Imma Poison Jab you and it's Toxic, and it works 100% of the time, and screw your Magic Bounce. In fact, screw it completely, it's gone now! Honestly, Poison types are going to be really good and in particular fantastic for punishing Ability-reliant Pokemon. Also, a question; does Poison Touch count for the "100% chance and Toxic"? Because Toxicroak Fake Outing into things is just evil at that point, if so.
Yes, Poison Touch is affected, as it makes contact moves have a chance to poison.
Tempered: Steel types are more obnoxiously bulky than ever. I'm assuming this applies to the Pokemon that is Steel type, and not just super-effective Fighting, Ground, and Fire moves?
You are correct. For instance, Empoleon takes reduced damage from Electric-Type attacks.
Incinerator: For clarity, does the Knock Off comparison extend any further than "removes item, and not items that cannot be removed" ie does it get a 50% damage boost if it burns away the item? In any event, this helps the utility of a lot of Fire types that lack Knock Off, and can potentially help even the ones that have it since they can consider dumping Knock Off in favor of assuming their Fire STAB will get the job done. It especially makes stall-y Heatran obnoxious, since spamming Lava Plume is not only liable to Burn but also liable to wipe your item, all while getting in damage.
The attack's power is not boosted.
Purity: Does it clear Toxic Spikes only if the Pokemon is grounded, or does it clear Toxic Spikes period? Regardless, this makes bulky Water types amazing, since Toxic can't clear them out and they heal passively even if they aren't carrying Leftovers/you get rid of their Leftovers. Belly Drum Azumarill will actually be getting back HP each turn that passes! I'm especially interested in seeing how Alomomola performs in Type Attributes, since it gives it notable advantages over Chansey, reducing the degree to which it is "bad Water type Chansey". Also, is this literally the same thing as Aqua Ring (As in using Aqua Ring will fail, and it can be Baton Passed) or is it just a passive healing? The difference is pretty crucial.
1. For simplicity's sake, it will always clear the Toxic Spikes.
2. It is literally the exact same thing as Aqua Ring.
Seedlings: Nothing will ever run Leech Seed again. (Well, maybe Smeargle, but I doubt it) This in particular makes Grass attacks a very safe move to use, bizarrely enough, since even something doubly resistant will hate being Super Seeded. Are Grass types immune to Super Seed just like they're immune to Leech Seed?
Yes, Grass Types are immune to Super Seeding.
Sub-Zero: Note that everything that resists Water is vulnerable to Sub-Zero Ice moves. Stallrein gets both Purity and this, and has perfect coverage offensively. (Well, almost perfect coverage -Thick Fat Walrein itself is resistant to both Water and Sub-Zero Ice) Stallrein is going to be ridiculously good, between excellent passive healing (Which it can supplement with Hail-backed Ice Body and Leftovers! 3/16th HP each turn while your enemy loses 1/16th? Yes please) Cloyster is another noteworthy, since a Shell Smash run isn't slowed down at all by switching in a Water type. And OK yeah Lapras and Dewgong benefit too whatever. (To be fair, stall Lapras is pretty plausible) Also, is "this Pokemon takes not-very-effective damage from Fire attacks" merely a poor framing, or do you in fact mean that being Ice type alters the Fire interaction to always be singly ineffective even if it should be neutral or double ineffective?
This was worded poorly in the OP. The effect should be interpreted as a change to the type chart, such that Fire-type moves are not-very-effective against Ice-types when the target is an Ice-type (which is, obviously, any time it would matter).
Legendary Entrance: To clarify; does the Twister behave exactly as actual Twister, ie ineffective against Steel, super effective against Dragons, useless against Fairies, capable of hitting Pokemon that are mid-air and doing doubled damage in the process, and getting STAB because the user is of course a Dragon type? Or do you mean "40 BP attack"? For that matter, from a Doubles/Triples perspective, does it spread? Regardless, this is a great way to break Sashes, Subs, Sturdy, and Multiscale (You know, other than the fact that Dragonite will probably just kill you with Dragon Claw/Outrage/Draco Meteor), finish off weakened opponents without giving them a chance at even an increased priority move move ("[name] held on with its Focus Sash! Dragonite switched in, its Legendary Entrance stirred up a Twister! [name] fainted!"), and just general chipping damage for absolutely free. Thank goodness there's no Dragon type Regenerator -that would just be heinous.
It is literally the exact same as an actual use of Twister.
Dirty Tricks: Again, clarification; is this in every respect identical to Taunt, or is it a pseudo-Taunt in the same way that Intimidate is a Growl, only for instance Magic Bounce will reflect Growl but not Intimidate? If it's a true Intimidate-Taunt, say hello to the death of Stall, gg, everybody take their Chansey and go home. If it can be blocked by Magic Bounce, that helps, though it's still an enormous hit to stall. Regardless, very very very influential, arguably more distorting than Stealth Rocks in Standard.
It is exactly the same as Taunt, so it can be Magic Bounced.
Benevolent: Regenerator Wish Core! Wigglytuff, Aromatisse, Azumarill, and in Ubers Xerneas are by far the most notable Fairies regarding this effect, with a minor round of applause for Mega Audino (But really it's just crappy Wigglytuff), since no other Fairy breaks reaches 100 HP. Even so, free weak-Wishing when you're switching Sylveon, Mega Gardevoir, etc is still pretty good, especially since unlike an actual Wish it isn't blatantly telegraphed a turn ahead of time. A question though; does it stack with an actual Wish, or does the Wish override Benevolent's pseudo-Wish?
Benevolent is entirely separate from Wish (it simply behaves in a similar manner) and therefore it stacks such that if a Fairy-type were to use Wish and then switch out, its replacement would receive a net HP heal of 83% of the "benefactor"'s maximum HP.