add more impact to the swing as if you aren't swinging a cardboard stick(you can do this by not using only your arm to swing. You have to use the entire body. if you want the sword to jab make sure the arm is straight other wise it looks like you're poking somebody with a pencil. make sure to add overlapping action and drag to make it look more fluid. slow in and slow out helps too. also add anticipation to give a hint to what the character's going to do next(example: lift the sword up before swinging or moving hand back before jabbing) for extra information watch the 12 principles of animation by alan becker on you tube or search up about it
