I think that up to this day the only enemy that i really haven't learned how to fight is Blitzes, i know that the main reasons for this are two: i suck at RGing in DMC4 for some reason, my DMC3 habits of RGing kills me and for the most part i press the button early than i should, i'm still up to learn how to RG properly in DMC4. And because i don't know how to make good use of Lucifer, it pretty much destroys Blitzes "barrier" if used properly and clear the path for you to damage them in any way you want.
For all the enemies in DMC1 i have a good muscle memory for their cues and their counters (and DMC1 in general is slow-paced), Shadows are not that much of deal seem that they don't have really quick attacks, most of their attacks have "long" cues and you generally have two ways to defend yourself: do some move to make youserlf safe or do the right move in the right timing to be able to counter them (i.e. jumping on their "spear-thing" and shoot or rolling in the exact timing when they use that homing move and follow up shooting).