World's 'Most Monstrous Bodybuilder' Dead At 36 After Heart Attack

Illia "Golem" Yefimchyk -- known by many as "The Mutant," and dubbed the "Most Monstrous Bodybuilder" -- has sadly died following a heart attack.

According to local media in Belarus, "Golem" suffered a heart attack on September 6 while at home with his wife, who tried all she could to save her husband ... performing chest compressions while waiting for first responders to arrive.

Yefimchyk was flown to the hospital by helicopter, where he slipped into a coma. His death was confirmed on Wednesday on social media by @whoisthebestbb.

"I spent every day by his side, hoping, and his heart started beating again for two days, but the doctor gave me the terrible news that his brain had died," his wife Anna said.

"I thank everyone for their condolences," she said. "It's very heartwarming to realize that I am not left alone in this world, and so many people have offered me help and support.''

Weighing in at a whopping 340 pounds, Yefimchyk achieved great heights in his career as a bodybuilder ... without competing professionally.

"Golem" amassed over 300k followers on Instagram, and was very popular on social media.

He once hit a 600-pound bench press, a 700-pound deadlift, and a 700-pound squat. Yefimchyk also ate seven times a day, consuming ~16,500 calories, reportedly consisting of five pounds of steak and 100+ pieces of sushi.

He was 36 years old.