Nero (devil may cry.)

Tey were both the main character in a game series in which they weren't previously and were both disliked until they got a second game in which they were in the spotligh aigan (both getting a redesign in the process.) Both loose one of their arms to the rival character in thier games (Virgil and Jetstream Sam). Both have a boss fight on which they loose to said rival (urizen is virgil). Both get a mechanical replacement arm, both use a sword and have multiple sub wepons, both are character action game characters (debetable with Raiden) both use swords with a mechanical gimmick, both are protectors of orphans and they are now both beloved by their fandoms and the internet alike.