[SPOILERS] Need help with Abaddon boss fight.

[Niskus]

I dispatched of his dragon form really easily and his angel form but I can never win the click battle... No matter how much I mash the key, he keeps winning it. I get him so low that even one measly hit puts us back in the sword clashing for button clicking but still can never beat him out.

[GUERRA]

I have the same problem

[Papaya]

I don't know if it works but you could try to lower the resolution. This helped me with bugs that were caused by the game not recognizing information fast enough (wich seems to be the problem here as well)
If this doesn't help you you could try to use a cheat tool with a speed hack (if cheating doesn't bother you as much as not being able to finish a game)

[Niskus]

Originally posted by OK OK OK:

I have the same problem

so I managed to find a thread online and it said to bind the alternate key for attacking to a keyboard button that you can hit easier and it worked so you might try that