What is the best two-unit combo you can make using all available units in the game?

You can use any unit, but it retains the FU stats of the original civ. For example Cataphract never gets bloodlines or blast furnace but keeps it's trampoline damage.

My picks-

Mamelukes with Korean Siege onagers, Cataphract and Genoese crossbowman, Jannisary and Huskarls, and Longbowman + Kamayuk. I feel like all of these combos would be insanely difficult to counter.

The true best may be Khmer Scorpians and Korean Siege onagers though, but that's almost cheese. Idk how you would stop that.