Carlos is a playable character for a segment in main game.
Carlos can fight with Nemesis in his second form in the Clock Tower. He can't completely defeat him, but he can knock him down and during Jill's fight with the monster, it'll lack of around 40% HP. Depending on whether the player chooses to fight Nemesis or escape from him, Carlos will say different lines to Jill in the cutscene in the chapel.
As Carlos, the player is more likely to die due to running out of time; it takes more time to kill a single monster with either the carbine or the handgun than with another more powerful weapon.
Resident Evil: The Umbrella Chronicles
Carlos is a playable character in Resident Evil: The Umbrella Chronicles. He and Jill Valentine are the available characters for the "Raccoon's Destruction" scenario. His handgun is the "Handgun SG". On the select equipment screen, the Submachine Gun HP will be defaulty selected for Carlos. His melee attack involves him using his machine gun to attack three times in a row to knock the zombie away.