__________________ Chicken Boo, what's the matter with you? You don't act like the other chickens do. You wear a disguise to look like human guys, but you're not a man you're a Chicken Boo.
I don't disagree with the consensus so far; Thor/Loki and Superman/Lex are great choices. But I'm surprised nobody's mentioned the mutant duo, who have an entire event devoted to this idea (Onslaught). In terms of covering power gaps and lack of redundancy, they're a better fit than Thor/Loki, even if the Asgardians would have more overall power.
I'm glad Digi picked up on the redundancy angle. It's why I didn't include Doom and Reed, because while Doom brings magic to the table, they're otherwise the same guy, and it's debatable if they'd even be able to accomplish much when teamed up given their vastly different styles. Even if he were partnered with Reed, Doom would probably still be more concerned with showing him up than solving whatever problem they had.
I'm not asking who would be most powerful together, because obviously Batman and Joker wouldn't even be a relevant option. I'm asking about what combination would most improve the performance and overall effectiveness of the constituent parts.
I think Batman and Joker is an interesting one because if the Joker were either somehow reformed, or in a Hannibal Lecter consultant position, he could really help Batman consider an incredible new array of angles with each case and problem, as well as a lot of unhelpful nonsense.
__________________
“Where the longleaf pines are whispering
to him who loved them so.
Where the faint murmurs now dwindling
echo o’er tide and shore."
-A Grave Epitaph in Santa Rosa County, Florida; I wish I could remember the man's name.
Actually Reed and Doom have worked together and done fine in many occasions. Most of these team ups will be slowing down one guy to benefit the other. Lex is just inferior to Superman, he can bring some cute tech but his overall tenacity comes from not holding back, which is something Superman can technically do but refuses to.
I'm just saying that people are overhyping Lex and Kal, they are powerful on their own right but as a very wise poster said Clark and Superman is much scarier