One Piece: From the Start, I Invite Luffy Aboard

[Joining the crew + decisive and ruthless + special abilities]

(The original plot may take up a little more space in the first thirty chapters, but gradually fades later. Feel free to skip parts.)

An explosion erupted beneath his feet, sending Usopp rocketing skyward. “The Straw Hat Pirates' number-one breacher, reporting for duty!”

Luffy: “Ouyang, put some armor on me! I'm going in!”

Zoro: “Ouyang, throw up some smoke! My blade is thirsty for blood. I'm going in to cut people down!”

Sanji: “Oho! That female ghost is gorgeous. Ouyang, give me more!”

Chopper: “Take this, reindeer elbow strike!”

At the Paramount War, a bunch of pirates with wildly different styles barged in and turned this serious battle into utter chaos.

Note: The author's skills are average. Give it a read for fun; if you like it, read a little more. If it's not your thing, please go easy on me in the comments. Thanks!