I don't really know if I'm the right person to ask for critique since I'm not a proffesional artist by any stretch of the imagination, but I'll try:
First of all it's clear that you know how to draw, you have all the basics down pretty much. Like seen in "monster invasion". You should probably practice drawing the human body a little more, especially proportions of body parts ( I'm having a hard time with that aswell). Other than that just keep practicing. Try out new stuff, maybe more background on your drawings, maybe different techniques and other materials. Stuff like drawing needs time.
I hope that was helpful at least a little bit, good luck in the future!