His sister started training Brazilian jiu-jitsu when Marcus was 14 years old, forcing him to come along to the gym so their father Clayton could keep an eye on her.

[5] Subsequently, Marcus and Clayton started training jiu-jitsu also, leading both to become black belts and the latter winning IBJJF Masters World Championship.

[8] Despite talking about transitioning to mixed martial arts since 2015, news surfaced four years later on July 30, 2020, that Almeida had signed a multi-year contract with ONE Championship.

[9][10] He has been training mixed martial arts at the American Kickboxing Academy and has competed in the heavyweight division.

[10] In August 2020, Almeida had to withdraw from an upcoming BJJ match with Fabrício Werdum due to a knee injury that has also delayed his MMA debut for ONE FC.

[12] Unfortunately, Almeida was removed from the card and replaced with Alain Ngalani on 13 January 2021, reportedly due to suffering an injury in training.

[25] He won the fight by a first-round technical knockout, stopping Carson with ground and pound midway through the opening round.