Tanks specialize in soaking up damage, either to get close enough to smack the heck out of their targets, or distract targets so that Blasters can fire into battle with a degree of impunity. Tanks focus on defensive powers like Amazing Defence, or Ability Enhancement: Constitution for the Hit Points and increased Saves. They also tend to take one, solid, mêlèe attack, such as Energy Attack: Concussive or Natural Weapons, the latter of which is arguably preferable because it cannot be affected by the metapowers.
The best Tank classes offer maximum HPs and/or other defensive abilities as well as some access to mêlèe weapons and attack forms. The Champion is the obvious choice, with a d12 for its Hit Die, its Iconic Attack, and Bombastic Aura, although that class requires that you increase your Charisma to take maximum advantage. The Warrior or Soldier‘s strong combat attributes are also attractive: d10 for Hit Dice, good BA, access to many proficiencies, and bonus feats (from the Warrior) or Sneak Attacks (from the Soldier). An overlooked option for a Tank is the Martial Artist, who specializes in mêlèe attacks, and therefore might not even need Natural Weapons or an Energy Strike and can thus put more resources into defensive abilities, although they also require a high Wisdom to take advantage of their defensive abilities.
Tanks wade right into fights, accepting that it’s their job to take damage. They lay the smack on anything that gets in arm’s reach and they give other, less rugged characters the room to operate unaffected by combat. It’s a dirty job, but somebody gets to do it!
Ability Enhancement: Constitution +5 10CP
Amazing Defence V (Defence +5) 5CP
Amazing Deflection V (Defence +5) 10CP
Natural Weapons: Improved Damage II (3d6), Single Natural Weapon, Super Natural Weapon 5CP
Combat Expertise (Improved), Defensive Martial Arts, Endurance (Diehard), Great Fortitude (Awesome, Supreme), Light Knockback, Origin Resistance (Improved), Super Strike, Toughness (Hard to Kill, Swift Healing), Unshakable (Fearless)