Probably Revan, but I'm open to being convinced otherwise.
MYT
MythLordDiamond
Gravid is largely unknown, so I'm not sure.
DAR
DarthAnt66DarthAnt66
Revan pretty easily.
QUE
~Quesin~Restricted
Gravid is at least several generations more powerful than Bane, due to the nature of each new Banite generation growing in power. Presuming that he can handle a lightsaber to a decent degree in addition, I find it rational to deduce that he would challenge Revan to a good fight, but not win.