Lavigne is a female Grim Reaper with a punk rock, tomboyish attitude. Her Reaper God's Crystal inhibits her scythe, which she will slash at her enemies with, slowing them down if they are hit. It also allows her to drain her opponent's energy if she touches them with her bare hands. She can summon black holes to throw at her enemies, sucking them in and allowing her to slash at them. 

She also can use her scythe as an electric guitar. She just needs to flip it horizontally, and if she plays air guitar with it, through some kind of magic (even she's not sure how it works) actual electric guitar sounds will come out of it. 

For a reference voice or personality, think of a punk girl.