The cannibal giant can only be hit after he throws his spiked shield. To avoid the damage from the shield, you have to make sure it hits an obstacle - it's otherwise completely undodgeable. After he throws it, you can shoot his weak spot, the giant target on his stomach. He moves too slowly to really catch Albert, so you're not in a lot of danger from him, but he has a mountain of HP and you're struggling to chip it away.
Junk Thardus's weakspots are not always obvious, and it has several phases. While its attacks are fairly easily dodgeable, for some ungodly reason, the devs saw fit to shut off your healing for this fight. Even worse, its second phase spawns ghosts, and its third phase gains an ungodly fast shockwave attack.
The Saboteur requires you to stun him by shooting out the generators in the boss arena. This is easier said than done. Every time you shoot out a generator, it needs some time to recharge, and the saboteur can shoot them to stun Albert. Even under the best of circumstances, the boss stunning only works about half the time. All the while, the saboteur is running around the arena blasting at you with his Hand Cannon.
Albert's reaction to discovering that the first surface world was actually another underground facility was quite appropriate. But the reaction was still devastating hilarious when it was meant to be dramatic.
Shocking Swerve: The reveal that the "surface" is in fact just a larger underground vault, with many of the buildings in it being nothing but facades, raises the questions of 1) why some of the buildings aren't facades, 2) where the cannibals came from, and 3) what possible purpose the city could serve that Glory couldn't perform itself.