Great gladiator

Answer from: NiceGuy1
Well I have all the Achievements so I know I have this one... But this Achievement is only about completing all the arenas with Brock, all three arena locations, 7 challenges each. If you have done so (on one profile, on one save game), you should have it. All I can suggest is to go to Brock, check each of the 3 arenas and double-check that you have the gold star on each challenge indicating that you finished it.

But if you're talking about green check marks, it sounds more like you're talking about completing levels (Chapters), of which there are 16, 20 if you add the 4 adventure packs. That's not what you need for this one. If this is the case... After Chapter 3: Rumbletown (which you should have already from the sounds of it), on the ship, go up the staircase on the right side and talk to the Goliath Drow there, Brock. He'll ask if you want to do an Arena, say yes. Again, there are 3 locations, 7 challenges each. Do them all, you get the Achievement.

Good luck!

Answer from: tannon
We did beat them all. got the charm for it. do i need to do them all solo

Answer from: NiceGuy1
Well I did them all solo, so that COULD be it.... I've played them with others, but I feel pretty sure I did each one at least once alone... However, that's more nit-picky than they usually go, and they'll all have stars so it would be impossible to tell which ones you still need to do. If you're determined to get this, I suggest starting a new game. Get far enough to get all the arenas (Rumbletoown, Chapter 3, isn't too bad, not too far, but you have to unlock the other two arenas as well). I know the third one is the Molekin-named chapter (Molekin Mountain?), but I can't remember the second... Maybe Troll Home Security, or the one after. The one where halfway through you get into Kaos' castle. Once you have all the arenas unlocked, play them all, one player only - I feel sure I didn't always use the same character, so that shouldn't be a restriction. Good luck!