One hit kill does work. It is the no cool down for bots that does not.
Please note that with one hit kill it also means YOU can be killed with one hit.
To make it work well, I recommend you use Deploy Anywhere, Unlimited Mana and turn OFF the one hit kill option. Then place your bot near the HQ, have it start attacking the HQ and just before your shots are about to hit the HQ, turn on the ONE HIT KILL option and you will then kill the base.
this works best with aerial bots and some Special bots. Worst with melee bots as you are likely to be killed as soon as you turn on One Hit Kill.
FYI: Never use ONE HIT KILL for resource fights or any battle that can be seen by the other side as you will be reported. This includes Elimination fights.
You can safely use for the ONE HIT KILL option for the weekend events though as well as raids but if you do too well in raids (and you don’t already have a reputation as a Raid master) then people will soon guess that you are using hacks and your own alliance will report on you.
I recommend that you always have the infinite mana on all the time (including reviewable fights) as long as you are not obvious about it. If I think I am too obvious then I quickly then just spam the abilities of my bot until at has done too many that it would not normally be allowed in a game. (IE. usually 5-6 times is enough) and when that happens the game crashes and no one will see your battle and you only lose 5FC but none of your bots will be on cool down.
This method is particularly good for wars.