[renowner]

Swift sidecut seems to do nothing. The in game tooltip says it can lightning critical, it can't.
It also can't be resized or anything. Just gives a cool sound and little lightning trail as you use it, doesn't seem to increase the damage, change the damage type, increase critical rate, or anything.

[Autumn]

increase critical rate

You might desire to check this again, the effect of Swift Sidecut is that it increases Critical Rate for the basic attack it performs. (It should be Redgull rank * 5, or 5 if you use a badge)

[renowner]

Alright you're correct, seems my crit rate from the front is 57% in the test, and 72% with sidecut from the front.