User blog comment:Eobard95/Black Siren and Deathstroke should go to Legends/@comment-26537965-20171022203427/@comment-26537965-20171025200243

Slade was under the influence of the Mikaruru, when he did that. Oliver released him, because he needed his help. As for Malcolm, the reason Oliver did not kill him, because he does not kill anymore unless absolutely necessary.