Slitherine

First Strike. what's the main differences? if a unit has the AC Hero, when it initiates, do the units Attack numbers now apply rather than defense? example would be the AC coupled with Provocateur, Crippling Blow, 1.5x or No Retaliation. seems like a perfect ambush setup even though your unit is in plain sight? does the same apply for First Strike?

First Strike = Strikes First before the enemy. Uses all of its attacks before the enemy. Exceptionally good for attack and defense. If the attacking unit has No Retaliation, then First Strike on the defending unit is wasted.

Aggressive Counterattack adds +3 to the attack value when defending. It doesn't have anything to do with the defense value. So if your unit has 12 HA and 8 SA, it will translate to 15 HA and 11 SA when defending. I haven't seen any stellar results with it. If the attacking unit has much higher initiative, First Strike or No Retaliation, it won't do you any good. A 'Meh' hero in my opinion.

Using Aggressive Counterattack with No Retaliation for ambushes will not work. The first is used when defending, the latter is used when attacking.

Rapid Fire 1.5x is always good.

Crippling Blow is only effective against full strength units. There are no guarantees that the attacking unit will be at full strength. In fact, they often aren't.

thanks I was hoping for another outcome whereby with AC the unit becomes the attacker and the attack Hero actiVATE.

I only use aggressive counterattack if there is just a free hero slot. To keep my army of hereos small I also like to recycle these heroes.
For me it doesnt really have some effect.