Even judged against the very low standards of the kinds of men who make the history books, it turns out that Portuguese explorer Vasca De Gama was not a nice man. Not nice at all.
Famously - well, I say 'famously', but this is the first I've heard of him - De Gama discovered a new shipping route from Europe to the Indian ocean, bypassing the Muslim controlled established routes across the Mediterranean or through Arabia. And, having found his way to the Indian Ocean, this unpleasant and incompetent man was thoroughly unpleasant and incompetent.
On voyage 1, en route, De Gama reprovisioned by attacking unarmed merchant ships and stealing what he wanted. In 1498 he reached Calicut and offered insultingly trivial tribute to the king, whose court laughed at him. De Gama took offence (and took hostages). He went back in 1502 and massacred sailors in port, sending their ears, noses and hands to the king. Some ships were burned, with passengers and crew dying aboard. The Portuguese conquered coastal towns and imposed colonial rule.
Bigger picture - if you ignore the piracy, the viciousness of attacks, the colonialism etc - the new trade routes undermined Venice's grip on the existing spice industry, especially bringing pepper to the masses. De Gama was nicely rewarded by the Portuguese monarchy. So, on balance, probably well worth the blood?