There seem to be two main issues here. What he's actually done in the past, and the fact that he minimised the issue for years (lying by omission) and let you think you could emigrate.
It sounds like he minimised and downplayed what he did, and you trusted that – when really his laundry list of charges could represent him inflicting pain and terror on innocent people.
For me, a lot would hang on whether his behaviour was towards other, equally violent young men, random victims, or women. Given he's been a good man since (you say) I think it would be safe to leave it in the past if it was other violent young men he attacked...but if he had been assaulting and imprisoning random victims, or women in particular – that would be a red line.
You really need to find out the full details of what he did before you can decide anything, I think.
The other issue is him minimising/lying for years, and letting you think you could move when he surely knew you can't... I could understand him not telling you immediately out of embarrassment and fear (even though he should have), but to not come clean before marriage? Before kids? It's not great. What else is he hiding, or lying about? How can you trust him? (Or, is it that he mentioned it, and you brushed it off as not needing to be talked about?)
I think he needs to be completely open and honest with you, to have a chance at rebuilding the trust. But if he's behaving like a good man now, cooperates/understands he never should've downplayed it, and shares the full details, I'd want to at least try to move forward together and leave it in the past.