What are the best champions that are good even when behind?

Janna you don't do damage either way so you can just throw tornados all day.

Most Supports.

Some champs have a larger margin they can be behind due to scaling well off of cheaper items (defense is cheaper than offense, magic pen items are cheaper than top tier ap items).

Syndra, Zed. You're still 100-0'ing enemies even if you are 0-2 and 25cs behind in lane.

most tanks or champ with heavy cc is good no matter how far behind. ex. and many more

Orianna is good even when behind due to the ridiculous amount of utility she has.

I feel as though stays relevant (as far as adcs go) provided you just build attackspeed and get a defensive rather than going for infinity and such as your %Max hp true damage is always relevant against tanks.

Any champion that can

A. Avoid being in combat range while still contributing (Janna's tornadoes, shields and ultimate)

B. Packs enough CC/Utility to always be useful (Alistar)

C. Potent abilities without gold (Lee Sin)

im not shure if he still works like that.

but it didnt really matter if you were behind on malphite. if you dont feed, its not so bad to be behind in cs. youll just hit a point, where your kit makes up for the slight disadvantage in items, and youll still be useful.

but that was before they changed and nerfed him a couple times.

{quoted}

blitz yes, yasuo no. lol.

Anyone with good AOE CC can simply afford a poor man's tank build and proceed to still be monumentally useful during team fights.

Wukong comes to mind in that regard.

Rumble doesn't need a lot of items to participate in team fight and doesn't have to win lane either.

Ahri does extremely well at singling out and shutting down a single fed enemy. With the stun from charm and the cumulative bonus damage from charm+DFG, she can easily blow up anyone, even a full-MR super tank.

However, against multiple fed enemies she becomes quite lackluster.

Typically champions with lots of utility. Cho'gath is a good example.

any support or cc tank.

Riven Zed Wukong Lee Sin.

All seem to be able to be behind/down and then still contribute a lot to team fights.

Anyone who doesn't really need items, just levels. Irelia with a TF can still do a little damage when behind so if you fall behind after that and go defense, it's not a problem. Non-tank supports more or less can work from behind, but supports like leona are screwed.

However many mids and virtually all ADCs are screwed if they fall behind and can't catch up.