Given how loud the accusations that Marvel can't do good villains tend to be, they've managed some truly compelling bad guy performances over the course of the MCU. Sure, there have been disappointments along the way, but when your primary objective is allowing good to triumph over evil, it's pretty catastrophically distracting to be faced with villains everyone wants to win.
Despite that, we have seen villainous excellence over the years under Marvel's banner. We've seen gods, monsters and surprisingly successful small-scale bad guys with personal vendettas and tragic backstories and each category has borne memorable characters.
The MCU's gallery of rogues is a many splendored thing, and while it's a little unfortunate that so many of them are killed off after a single appearance, Kevin Feige and his writers' room are growing with experience, learning the lessons of the past and ensuring their new bad guys live up to their heroes. To do that in a family friendly environment is no small feat.
The question now is clear: which villains are the best and worst we've seen in the MCU so far?
To qualify, they have to be more than a henchman: so right-hand men/women do count - provided they actually get their own chance to shine - but nameless nobodies like Kaecilius' Zealots who are there for cannon fodder really, really don't. And neither does Karl Mordo, because he's not really there yet.