1. Darth Malak
Malak is outclassed.
2. Darth Maul
Maul simply cannot not go pound-for-pound and blow-for-blow against Orbalisk Bane. Bane is too well protected, too strong, and too aggressive. Maul might be able to temporarily mount an offensive against Bane just like Raskta did, but it won't last long. Maul is very good on the defensive though, so he might be able to hold out for a while, but ultimately Maul's sabers will be useless against Bane's Orbalisk armor.
Maul has powerful TK, but Bane isn't Kenobi. Maul won't be ragdolling Bane and Maul has no answer for Bane's lightning.
Whether through sabers or force, in the end, Bane would win.
3. Darth Sion
Traya was able to break Sion, so he's not unbeatable. Just like Malak, Sion is outclassed.
4. Darth Tyranus
Of course, Tyranus is an incredibly skilled duelist who is known for his precision. It's not inconceivable to believe that Dooku could win a few rounds by scoring hits on Bane's unarmored parts, but I don't see him taking the majority. Bane's aggression and power would overwhelm Dooku just like Anakin did.
Force-wise, Bane's lightning is just plain better than Dooku's as well.
5. Darth Revan (before memory wipe)
I am of the opinion that Malak was not lying when he said that he surpassed Darth Revan, so I would give Bane the win here. I will also admit that my opinion contradicts Drew's, where he said that Revan, Bane, and Vader are all on the same tier. Drew may be an authoritative source, but his opinion is not canon.
6. Wrath II
I don't play ToR, but based on how others have described Wrath 2, I think Bane could pull off a win.
7. Darth Vader (ESB) and 8. Darth Malgus
I have Bane > Vader > Malgus. Unless Vader can somehow crush the orbalisks, Vader's strength will not help him here. Some might argue that Vader could ragdoll Bane with TK, but I'm not seeing it.
9. Exar Kun
Not sure, Kun is pretty skilled and powerful.
Boss. Tulak Hord
Tulak is too much of an unknown to judge.