I did this but it didn't work for either of them. Did you have to use a specific duelist? and does it have to be reduced to 0 while they're at 4000 or something like that?
I completed both in Tag Duels. It seem it just have to be lethal damage. Maybe it need to be at least xxx damage done to count? The minimum I did was ~3.5k
I just got the ra sleeve from killing a person in competitive matches using ra. It’s not a great looking sleeve though, it looks too similar to the dark Marik one imo