I was recentley playing Avatar BO1 Ranked draft and I had cast Ruinous Waterbending with the additional cost while my opponent had 6 total creatures and 4 of them were 1/1's. After the spell was cast however only 3 of the 1/1's left the board and one stayed as a-1/-1 and I did not gain life for said token but it appeared as my opponent couldn't use the token as though it were on the board