For City of Heroes Tankers, the secondary powerset is the source of offensive powers or attacks.
Battle Axe - A combination of single target and small area of effect attacks.
Dark Melee - Mostly single target, dark melee has fast hitting, fast recharging punch type attacks.
Dual Blades - This set relies on combos to deal much of its damage. The set is poorly designed and ends up being weak.
Energy Melee - The highest single target damage by far. You can approach scrapper level damage with this set.
Fiery Melee - A weak, badly flawed set at its core. The secondary effect (DoT) is unreliable and random. The attacks are slow animating and do poor damage.
Ice Melee - One of the two completely broken offensive sets for tankers (the other is war mace). It had crowd control aspects as part of its design, but controllers are so powerful that these are not needed.
Stone Melee - This set has excellent single target attacks and some minor area of effect damage. The attacks chain together very well to create a fast, smooth attack chain with good damage. Second only to energy melee for single target damage.
Super Strength - This is a good all around set with single target and area of effect damage. Rage can be made permanent once slotted for recharge, and this adds 80% damage most of the time. Footstomp is the gem of this set - the best tanker area of effect attack. Footstomp alone has made me renew my subscription to City of Heroes more than once.
War Mace - The second of the two completely broken offensive sets (the other is ice melee). It is really just a mess and always has been.