Review the item:
Mike loves to play computer games, especially Tomb
Raider,
he imagines that all the villains are his problems, and he gets great
satisfaction blasting them to bits.
The problem occurs between Raider and he. Mike loves to play computer games, especially Tomb Raider is a complete sentence. He imagines ... begins the next complete sentence.
Because these two parts have a comma alone between them, they create a comma splice, a major sentence error.
To fix the problem, you could put a period after Raider and then capitalize the H for he.