DBD Tier list assuming the Killers are using their strongest addon combination
Here's my tier list assuming that the Killers have their strongest addons equipped (in my opinion):
Keep in mind that I don't really play much Pig, Plague, Doctor, Myers, Ghostface, Legion, Wraith, and Freddy so I had some trouble placing them on the tier list. Feel free to comment on what you agree/disagree with!

Comments
Myers should leave it in A or B, his tombstone plus Judith's memorial is too powerful.
TWINS? WHAAAAAA-
Yup, I play a lot of them so I know how powerful they can be in the right hands. Their ability to slug and camp is one of if not the best in the game and with addons like wooden sword and the purple addon that makes victor faster they become incredibly powerful. The only reason why I didn't put them in SS tier is because if the survivors are competent and know the counterplay to them then it becomes a much more difficult match for the twins to win, but not impossible.
I guess I should've put him higher on the list, I completely forgot about how busted tombstone piece and J. Myers Memorial is. With that combo he belongs in B+ Tier.
Plague so low? The Black Incense alone is enough to make her OP. Combine it with an emetic or the severed toe, and you'll have almost permanent wall hacks+permanent one shotting.
Myers Scratched Mirror, with an indoor map offering and he is A+++. Such fun too!
Myers with J.Myers and Tombstone Piece is easy S-tier IMO. It's just OP af.
Bubba with double chili add-ons or award winning chili w/ engravings is easy A-tier.
Plague w/ Black Incense is just dumb IMO. A-tier.
Wraith is a candidate for A-tier with silent bell and all-seeing.
In my opinion I would leave it in Tier A if I had Tombstone Piece along with an addon to increase stalking, I mean, I have been testing it many times with Tombstone Piece and the most normal is to kill 2 survivors with it and the maximum is to kill 3, if I put Judith's Tombstone together with Fragrant Tuft of Hair it would leave it in Tier C + and in Tier B it would leave it if it had Jumpscare Myers addons.
Freddy is not A tier he is C tier if you pick the strongest addon for each character