The only time ambipom ever becomes an effective revenge killer is when your opponent runs out of options to switch to. If they can switch to something convenient, Ambipom is terrible, or at best, no better then any other fast, hard hitting Pokemon. At least for revenge kills. It is however very effective at doing it's thing with a lot of punch and getting the hell out of there. It's also good for scouting.
Dugtrio on the other hand is a much better revenge killer. It almost always does not matter what HP is remaining for the opponent, because chances are they will die anyway. Blissey, Infernape, Jolteon, Electivire, Lucario, Heracross (Non Scarf), Tyranitar, Alakazam, Magnezone, weakened steels... It takes on a lot.
Weavile is good at revenge killing anything weak to dark assaults. Gengar, Alakazam, you know the list. So I don't think it is as effective as Dugtrio in that regard, but it does do it's job. I find it too predictable otherwise though, and too easy to wall.