Anyone have some ideas but what creatures I should use or what books I should look in?

Rancors.

For defeatable, sentient opponents, Wookiees, Trandoshans, etc.

For creatures, It depends on how big you want to go, but Rancors are always fun. You could, of course, simply homebrew some species that already exist in Star Wars (like the Acklay or Reek or Nexu).

I’ve been working on a pit fight adventure using Raqor’Daan (dark wolves). They are featured in Lords of Nal Hutta pg77

20 minutes ago, P-47 Thunderbolt said:

Rancors.

For defeatable, sentient opponents, Wookiees, Trandoshans, etc.

For creatures, It depends on how big you want to go, but Rancors are always fun. You could, of course, simply homebrew some species that already exist in Star Wars (like the Acklay or Reek or Nexu).

All those you mentioned existing also exist in the books. So here's stats for an Acklay, http://swrpg.viluppo.net/adversaries/creature/2639/ . The Reek is in Allies and Adversaries page 135. And here is the Nexu, http://swrpg.viluppo.net/adversaries/creature/1163/ . They all make for pretty good foes.

Ah! I don't have AaA yet, so I didn't realize they had been officially statted. Another one to consider is the Wampa, officially statted first in Strongholds of resistance. More manageable that a rancor or acklay, but still not something you'd want to mess with.

If you can find it, the Creatures of the Galaxy adversary deck should help.

Whaladon

Are you looking only for creatures or combatants in general?

Also, you need to throw Black Krrsantan (wookiee from doctor aphra comic) in there from allies and adversaries, his background is as a pit fighter. page 70

10 minutes ago, KRKappel said:

Also, you need to throw Black Krrsantan (wookiee from doctor aphra comic) in there from allies and adversaries, his background is as a pit fighter. page 70

That would be a fun background lore incident (if the campaign is in the right time period), especially if everyone playing is super into the lore and knows about Krrsantan. "Oh, by the way, your opponent today is a black wookiee known as Black Krrsantan, a rising champion in this arena circuit." "Is it to late to back out now? I value my limbs."

Cyber-rancor

An enslaved Jedi

Bulk-purchased battle droids

A heard of starved loth cats.

An old clone who still has it.

A deshade

Pretty sure this is Legends, but I used a Vorantikus in an arena setting:

Pretty much any beasty would be good for pit fighting, especially if they are known to be hostile. What you should pick, should depend on your players and their capabilities.

Gundarks

A Gundark, a Rancor, and an Acklay walk into a ba- umm, pit...

Shockboxers.