Mario bores me...

[Marth]

Pretty sure Fawful is dead... um spoilers.

Yeeeaaahhhh I kinda haven't beat ML3 yet...
But eh I doubt he's dead, that's too extreme for a Mario game. Bowser's been dropped in lava on multiple occasions, turning him into a skeleton (AKA Dry Bowser) and he still lives.

Um hi, before he was a main villain he was Cackletta's underling. She not only died but you DESTROYED her SOUL. You physically killed her, Fawful then placed her soul in his headgear and then had her possess Bowser to form Bowletta. She then eats you and you fight her soul. You don't just kill her, you wipe her out of all forms of existence. Now that's extreme.

Spoiler

and Fawful commits suicide. After you beat his soul(a reference to Cackletta's death) he says something along the lines of going into the dark forever and taking you with him. His soul then self destructs and Fawful is no more just like his mistress. These are dark turns for Mario games but personally I thoroughly enjoyed them.