Take a look at the sentence again:
Mike loves to play computer games, especially
Tomb Raider, he imagines that all of 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.