Game: Comix Zone
How To Beat Him/her: Granted, you probably didn't even make it past the first level, let alone the first boss. (Don't worry, we didn't either.) But, we're giving you the benefit of the doubt. What actually makes this final battle difficult is that we have to save Alissa before she drowns.
The most effective way to do this is to activate the switch on the second panel, which deals damage to Mortus. Be wary of his attacks because they do a lot of damage. It doesn't matter if you take out Mortus or his creatures first. Once you've taken both out, hit the switch on the third panel. This will free Alissa and complete the game.