hi...I'm designing a game and came to an halt let's say character X hits Y...Y reacts by looking like it's been hurt (I mean the model switches up to the 'hurt' animation) but it looks empty...Y doesn't look like it suffered enough I began checking 3D games to see how they do it, and noticed that when something hits someone, there's always a special effect coming with it... some sort of glowing spark where the hit was taken now, I'm trying to design such an effect, but just can't... how I am supposed to do it ? make a 3d model for the 'hit' effect ? go 2D ? is there some existing model I can use as a base ?

That effect is probably a particle effect - meaning it's the programmers responsibility, not a part of your model.

it could be an particle FX but you can also make some FX like a 3D artist. an example: you can make a sphere and make it transparent and then you put on a fire or a lightning texture (so some parts are transparent some not) and animate the sphere(or other objects). these FX dont look relly good but could save some performance(depending on what quality FX you want)