Is there a chart somewhere?

it's not necessarily the maps though - it's the rest of the team composition

even the 'best' char for a map would fail with a shithouse team

There are still good and bad characters for certain maps
A lot of it is based on what flanks are available

tracer is hard to play vs junk rat

there's plenty of characters that aren't good on certain maps. close quarter maps you don't want to pick someone like widowmaker etc.

Most of the best of 3 control point maps are bad for snipers due to their small size and closed in control points. Other than that it is more of a question of where on the map you are then the map as a whole.

Thanks for all of the positive feedback!

Domination style maps. If you are big into supporting use junkrat from a distance and bounce nades off walls

i hate whoever came up with junkrat...

agreed