Maybe make a longer ‘charge up’ if you get what i mean. Maybe also make the actual sword swing faster. This last tip cant be animated but maybe add a script where when the tool is activated you add a trail to make the swing look even faster! One last thing, I think R6 fits the style of this game i would keep using it! Great work overall!
Assuming that is a great sword you should bring the start of the swing more over the shoulder and leaning back(lean the whole torso back) . It should give less of the linear effect
IMO, you should make a different type of easing style if you made an animation with it. Not just constant animation, you should do either Bounce or Elastic so it can be very appealing to the users.
How about making something like, the rig should charge up, like its bringing it more upwards, and then during the slashing, give it a bit more of a horizontal strike.