If you look under the character detail site and click on the 4* you want most people talk about who that 4* pairs with. There are also threads under character discussion that discuss pairings
The problem with that method though, is that the thread for each individual character might be 8 pages long and of those 8 pages, the first 4-5 are speculation from when the thread was labeled “Unknown” and people were guessing who it is. The next couple pages might be from when the character was disclosed, but details of their powers aren’t known yet.
Bottom line is that there is a lot of trash in those threads AND they’re really only relevant up to when that character was released. No one is going back to an old character’s thread to post an update about how they work well with a new character.
This is an old joke. Back when 4* Starlord was godawful, eeeeevery new character release - you know, those “interviews” that sound like they were written by Skynet - would suggest pairing them with Starlord to lower their costs. His yellow was an active that only lasted a couple turns which made this a universally stupid idea.