Parodied: Sara wonders aloud why the government doesn't just send Frederich to do all the fighting, seeing as how he can't die.
Zig Zagged: For the most part, Frederich is invincible. But at one point, one of the ghouls injects him with serum that negates his Healing Factor, and Sara has to protect him until it wears off. Also, Frederich can actually die if he is pushed off a cliff, pushed into lava, or water.
Averted: Frederich has a life meter, and once it runs out, he's done for.
Enforced: The developers don't want the game to suffer from quality due to people constantly losing because Frederich dies.
Lampshaded: "You know, Frederich..It's pretty cool having an unkillable partner. Sure beats havin' to watch your back all the time!"
Exploited: Sara has an entire moveset based around using Frederich as cover or a human shield.
Defied: The developers programed Frederich good attack AI so he does have to be babysat, but is not immortal
Deconstructed: Sara's model is stuck in a glitch while Frederich is getting hammered by a whole ghoul army a few yards away. Since he can't actually die, the player has no choice but to restart the level. Also, people exploit the game by sitting behind a corner while Frederich fights all of the enemies.
Reconstructed: The devs fix all those stupid glitches, and some bad guys deliberately bypass Frederich to attack Sara.
Played For Laughs: Frederich is largely useless in combat despite being immortal and having powerful attacks. He serves mainly as an excuse for Mook Chivalry as they flinch-lock him (the only one in the game who is vulnerable to that it in fact) to prevent him from pulling off moves that are utterly reckless for mortals but result in One Hit Kills. Cue Amusing Injuries.