I currently got three resplendant sparks from lilith,uber andy and completing the iron wolves rank.

Can i get my fourth by making a new character and defeating lilith again?

No, make a new character and farm wolves or drop Uber and salvage it

I did read a reply tweet from PezRadar that stated if you defeated Lillith in an earlier season you'll also receive a Resplendant Spark - so if you did that you should get a fourth.