I just want to reiterate that I created this thread with the idea in mind that you can post any piece of art, with the intention of accepting feedback and critique to improve your work and skill. Part of this is not saying things that belittle other's work practices, such as using references. The other part of this is that you are posting here to be part of a learning environment. If you already think you have mastered drawing, then please don't post here. It sort of poisons the environment to say things like, "I'm great at drawing." Whether or not it's true (it isn't).
Okay now for some critiques.
Red Fortune: You have improved significantly since you first started posting. One place for improvement in your comic is the environments, especially the interiors. You might try finding some refs to use, and brushing up a little on indoor perspective. Probably the best way to do this would be to sit in the corner of a few rooms and drawing them out in a mechanical sort of way. Just to get the big spaces down.
LegoLord: I think you need a better reference for that (his left) hand. It looks a bit detached. I think you would be able to see the ball of his wrist and probably at least part of his arm. Some of the proportions are wonky too, such as the hand should probably be larger. Compare it to the size of his head and you will see what I mean. Some of the shading, especially on the clothing, could benefit from the use of harder brushes.
Lofn: I like your stuff it has a lot of character. Do you ever draw with ink and brush??
OmnipotentGrue: I want to give comments but your scans are so light that it is difficult to see the process of the drawing.