Who is the strongest

Rengar isn't doing too well right now, since ADCs are harder to assassinate.

Rek'sai on the other hand is doing fine, so her I guess. I think she's boring as shit to play though, tbh.

Rengar, by like, a landslide.

Since you made two topics for some reason I'll comment on the one where the words are spelled correctly lol

Honestly I think it depends on what you like. Rengar is a good assassin but team fighting potential isn't that good if even there.

Rek'Sai can make some great early game ganks and is more of a team fighter with her knock up. I've always been a fan of her myself. She was the champ that made me like jungling.

Comparing an assassin to Rek'Sai is like apples and oranges. Both have strengths and weaknesses but they are totally different classes