Side-scroller sword combat

So I am making my game combat oriented. Basically the player has a sword and 3 different changeable spells. The game is a 2d side-scroller.

What I want is a dynamic combat but not too sure how to achieve it.

What i had in mind was to have 2 or 3 different attack types assigned on A,S,D and maybe even add a block or a parry option.But the problem with block or parry is that you aren't going to fight 1v1 (except against some bosses) you will fight a pile of enemies and it should feel like you are really powerful (not OP), and it should be fast.

So that is the general idea but I am not completely sure about it, do you maybe know a game that has done it already, I would like to take a look and execute it in my own way of course, or you might have something different in your mind? Any comment is helpful.

Cheers

Well, depending on the strength of the bosses, a block or parry may not be a bad idea for some strategic moves. Otherwise all you will have for the tougher bosses is "hit it until it's down". (which is okay for earlier bosses, but after the first or second one, you may want to add something in that would require a bit more "thinking" with your skills.)

Adding defense doesn't mean you have to sacrifice an offensive skill though. You can probably find some kind of magic skill that works offensively and defensively at the same time. It may not be the strongest move in the book, but the dualism of it would easily compensate for it.

Thanks for advice. I will definitely consider adding block or parry, but I have come up with a pretty cool combat system. Now I just have to make it heh...