Kurapika isn't stronger than Chrollo or Pitou. Alluka is very strong, but she has no physical strength, and her power only works if there is someone around her that she can request three things from.

I had a hard time choosing between chrollo and pitou, but in the end I think Pitou is stronger. Also on their wiki pages, Pitou's stats are higher than Chrollo's.

Either her or Neferpitou