Webbie -- I Made 50 Cent Rap For Me ... To Pay Off Boxing Bet

It turns out songs about killing people sometimes prevent violence ... 'cause Webbie says his $1 million boxing bet with 50 Cent is settled ... and all it took was 50 spittin' some hot fire on the mic.

As we previously reported ... Webbie's been peeved at Fiddy over a $1 million dollar wager the two made on a fight between Terence Crawford and Yuriorkis Gamboa last May.

Webbie's guy Crawford KO'd Gamboa ... but he claims when it was time to pay up 50 pulled a PSY (remember Gangnam Style?) ... suddenly disappearing without a trace.

It seems like things were gonna go all Biggie and Pac for a second ... (with Webbie actually threatening 50 on a recent track) -- basically telling him to pay up or else.

Well according to Webbie ... 50 paid his debt ... but not in cash -- payback came in the form of a guest verse on a track for Webbie's friend and label mate Lil Boosie.

"I told him we dont need no money man, we need some verses, get on my boy song."

Check out the video -- Webbie says 50 asked for a week to finish the song but Webbie demanded payment by that night or there was no deal ... and 50 acquiesced.