Hey! So, I'm not referring to imperialism / neo colonialism era. And obviously I'm not also asking about a guy who had white-saviour complex, once that's nothing but another tactic to justify colonization.
So, is there any record from the 16th and 17th centuries, that registered at least one white person genuinely disturbed by the whole processing of colonisation, or anyone who went loud about it or something - even if it wasn't their intention - ???
How about Bertolomé de las Casas? He was the first to condemn the African slave trade (after playing a role in establishing it for the sake of the indigenous peoples actually and not realising what he would unleash) - at least his writing is the oldest on record (according to Martin Neumann: Las Casas. Die unglaubliche Geschichte von der Entdeckung der Neuen Welt. 1990, S. 89–94.)
Btw: I would be careful to assign every white opponent of slavery a white saviour complex. That label should not be applied on a general basis but if it is useful at all than only after analysing the individual case.