Most folks would take one look at this fellow and say "Yup. He's the tank". And most folks would be mostly right. The Guardian is the most straightforward of the characters, and it's clear from his Ahhnuld-like build that he prefers to solve his problems by swinging a large chunk of sharpened metal at them. He's a healthy hunk as well, so he can absorb a lot of damage, and he's quite adept at carving out big chunks of his enemies' bodies with a comically oversized sword.
The Guardian isn't confined to up-close physical attacks though. Like every character in this game, he also wields a ranged weapon - in this case a cannon, which tears gaping holes in his targets but reloads slowly - and a selection of twelve magical and special abilities. The Guardian's specific powers tend to be elementally-charged physical attacks, usually (but not exclusively) cold-themed.
For example, he can charge his shield with electricity or cold and bash enemies into temporary inaction, fire off a poisonous cannonball, or send out a storm of ice shards that blast opponents backward. Conversely, he can taunt distant foes so skillfully that they can't help but charge, bringing them within easy reach of his sword.
Of course, most of that finesse goes south when he morphs into a giant, bear/gorilla thing and starts tearing things to shreds with giant, clawed paws.