MMA fighter Choo Sung Hoon made his terrifying return to 'Running Man' in the latest episode!

Featuring Yoo Jae Suk as 'Captain Running Man', HaHa as 'Iron Ha', Song Ji Hyo as 'Black Blank', Ji Suk Jin as 'Dr. Ji' and The Hulk, Kim Jong Kook as 'Kook-Thor', Lee Kwang Soo as 'Giraffe-Eye', and Gary as 'Spider Gary', the cast members delighted in their newfound superpowers.

However, the Avengers soon found out that they weren't alone. Joined by 2PM's Chansung and Taecyeon as the 'Twins', master martial arts artist Jung Doo Hong, and their archenemy Choo Sung Hoon as the 'fighter' (a.k.a. as himself), they found themselves facing formidable adversaries.

Finally, only the 'fighter' himself remained, claiming victory over his rivals and the defeated Avengers. However, not all seemed to be lost - the final few seconds previewed the continuation of the 'Avenger Initiative' with the announcement that a big battle was coming.

Check out the full episode below!