S rank

Dragapult: 252+ Atk Forretress Ice Spinner vs. 0 HP / 0 Def Dragapult: 100-118 (61.3 - 72.3%) -- guaranteed 2HKO. Can tera away the fire weakness, or at least live sturdy.

Dragonite: Ice Spinner and before that Rock Blast if you're loaded dice.

Garchomp: 252+ Atk Forretress Ice Spinner vs. 252 HP / 0 Def Garchomp: 164-196 (76.2 - 91.1%) -- guaranteed 2HKO. Offensive dies/goes to sash. Rough skin sucks but still.
S- rank

Gholdengo: 252 HP/ 4 Def or less is 2hkod by EQ.
A Tier:
A+ rank

Annihilape: Ok this IS bad for Forretress.

Baxcalibur: Rock Blast.

Dondozo: Hope it teras grass beforehand for pin missile. Still not doing enough but yea.

Hydreigon: Pin Missile ohkos w/ 4 hits all the time, same w/ 5 if it's bulky.

Kingambit: Hope it teras dark for Pin Missile. Alternatively Iron Def+Body Press, but not what I run.

Meowscarada: Best thing for Forretress. 3 hits is enough, so they re welcome to knock off dice.

Skeledirge: Eek

Volcarona: Tera the weakness away, live w/ sturdy, or hit the switch in.
A rank

Breloom: Overcoat gets this. Otherwise no real chance.

Corviknight: Very bad.

Garganacl: Iron Press can again do it, but that's it.

Gengar: EQ is a guaranteed ohko. I use tera dark, and since they can't choose poison vs. base that is essentially a guaranteed resistance if needed.

Hippowdon: Bad.

Magnezone: EQ.

Mimikyu: Well you could run a steel move. W/ my set Mimi doesn't like Rock Blast, 2hkos after disguise(or thereabouts.) Doesn't deal much either.

Rotom-Heat: 5 hits of Rock Blast on the switch, or 4 and then an ice spinner(to not miss,) depending on the rock blast dmg rolls.

Rotom-Wash: Eek. Maybe Seed Bomb lol? Actually that is likely to 2hko but there's tera so hmph.
B tier:
B+ rank

Azumarill: Yucky. Maybe Iron Defense, Azu's damage here isn't great at least.

Blissey: Body Press or forget it.

Clodsire: EQ 2hkos. Also you're a great switch in.

Espathra: Lol, whole reason I made my loaded dice set is Pin missile vs. Sub Espathra.

Glimmora: EQ. Immune to the toxic spikes itself.

Grimmsnarl: Well a steel move maybe. But this itself won't do much damage w/ standard moves, so it depends how your team does w/ screens.

Palafin: Seed Bomb maybe.

Pawmot: EQ. Sadly will probably only 2hko, esp. if they sash ofc, but they can't do that much.

Salamence: Idk how common fire is. Ice Spinner ohkos a Moxie switch in, and still does a lot to Intimidate.

Sylveon: I find this bad.

Tauros-Fire: 0 atk Tauros-fire won't ohko in case you're not sturdy or SR is up. EQ still does a bit...not a good match up neccessarily.

Tinkaton: EQ