Watched it a couple of years back. About a guy who lived on an island nation that got invaded by a foreign country and somehow he got transformed into a monster and fought against the invaders. Dont remember if he won or not but after the fight he got smuggled out by some merchants in a flying ship. On his journey he meets some other people who can transform and in the end he defeats some kind of ultima badie.

Its been stuck in my head for weeks now and i havent been able to find it, so thx to whoever can tell me what anime it is...

Sounds like Bounen no Xamdou

~4400 manga completed
~1700 ongoing...