I'm sure I just jumped on some bandwagon or other with this, but honestly
Jim Moriarty from Sherlock
and the latest incarnation of the Master from Doctor Who
are totally soulbros.
They could have a spinoff together ("Gee, Master, what do you wanna do tonight?" "The same thing we do every night, Jim - try to take over the UNIVERSE!"
) aaand... uh, for all I know, they already have their own section at FanFiction.net and twelve fan groups on DeviantArt, I mean, their fandoms are huge and I'm a bit late to the party anyway, so, no matter what I come up with, someone must have thought of it already