KSI defeated FaZe Temperrr in the main event of a huge Misfits Boxing event held at London's Wembley Arena.
After winning two fights in a row back in August, the British fighter made his comeback to the ring and turned on the style to stop the Brazilian within the first round to advance to an epic meeting with Jake Paul.
The 29-year-old was defending the cruiserweight title of his Misfits Boxing organisation, which specialises in fights involving young fighters better known for their online personas. Temperrr was knocked out in the final minute of the first round by a left hook.
Faze Temper came into the ring with a 2-1 record, coming off a first-round KO victory against Overtflow, with his sole loss coming to Slim on the first Misfits x DAZN night.
With a 4-0-1 record going into this bout, KSI promised to finish it off in a big way and move closer to the mega matchup with Jake Paul.
"I had a new technique and I wanted to show it – and damn, it worked," said KSI, speaking to DAZN
"No disrespect to Fournier but I want Jake Paul. That's the end game. I said I wanted it by the end of the year and I will get it."
KSI was supposed to take on MMA fighter Dillon Danis, but the two-time UFC champion Conor McGregor's training partner withdrew with barely 10 days' notice.
KSI and Temperrr, topped a lineup that attracted a sell-out crowd to the 12,500-capacity.