I agree also. Using a spell like Sickness or Abomination to deliberately de-buff a unit is killing.
If I choose to attack a strong unit with one of mine, get it down to 1 HP, and then use Abomination’s arrive ability to wipe it off the board it should still count as killing. In this instance, I could not have used Abomination first, because then my own unit (which would have also been affected by the debuff) would not have had the attack power to finish it off.
However, this unit is directly under my control.
However, Sacrfice the weak forces the OTHER players to destory a unit (Each player sacrifices their weakest unit.) So the only unit you destroy is your own, and they (other players) destroy the other. (In my head at least). As it’s not their turn, they don’t get rewarded, and you won’t get bounty for killing your own unit.
Two step I think is different as well. If you destroy a partner (A), and the other partner (B) dies due to de-buff, you should only get rewarded for the one you destroyed (Partner A). It was not your unit that killed the other partner, or your unit’s ability. It was the drawback of another players spell.