Hank Pym, confronted by Loki disguised as Nick Fury, admitted to killing the Avengers Initiative candidates and Thor.
The reference text clearly states that Hank Pym admitted to the killings. His motivation stemmed from perceived retribution for his daughter's death. He targeted individuals associated with the Avengers Initiative and Thor, viewing them as responsible or connected to the events leading to his daughter's demise. Therefore, based on the provided source material, the definitive answer is Hank Pym.
