Best duo characters

I play with a very small group consisting of 3 total players, including the DM, so to make the game more fair I play two characters at a time. What would be the best theoretical duo of characters to play together?

I will likely not use any of these, as I don’t power build, but I’m just curious on what it would be. I would love some good but not over-build characters as well!

Please no Spoiler, especially for Curse of the Crimson Throne! Thank You!