I think your character is lacking tertiary detailed like wrinkles on his clothes. I'd assume there'd be wrinkles on the pants, especially where the pants meet the feet/shoes. Speaking of shoes, his left shoe/foot looks a little weird. I'd recommend finding reference of a man wearing a similar get up. And looking at martial artist shoes and how other pixel art characters draw feet. Right now your foot looks a little "mushy".
Your limbs look a little mushy and stretchy too. I'd recommend checking out some anatomy images to help you with the body. Something about the arms look off to me. I'm no anatomy master but the placement of those elbows and length of the arms look off to me.