CASPer Alamo (The Revelations Cycle, #9)

CASPers—Combat Assault Systems, Personal—are the lords of the future battlefield. The massive mechs were created to give humanity an edge against the rest of the mercenary forces in the Galactic Union.

Just like today's tanks, though, massive amounts of armor and weaponry just make the CASPers "hard to kill," not "invulnerable." There are things in the galaxy even stronger than the CASPer, and when Humans run up against them, it's up to the Human inside to figure out a way to snatch victory...