Vido Santiago is one of the two founders of the Blue Suns mercenary group and ultimately it's sole leader following his betraying Zaeed Massani. In contrast to Zaeed, who is ruthless but not completely bereft of a conscience, Vido is completely amoral and cares only for himself and his profit.
Vido Santiago and Zaeed Massani were the cofounders of the Blue Suns, with Vido being the book-keeper. Though for a time this union worked well, as time passed it became increasingly clear that the two had differing views of how to run a mercenary group. Many times Zaeed's moral standards prevented Vido from making money, and after a point Vido decided he'd had enough. Turning on Zaeed, he personally shot him in the face and took over the Blue Suns as it's sole leader. Zaeed, having survived the shot, swore revenge, also later noting that under Vido's singular leadership the Blue Suns only got worse. Indeed, Vido's many criminal acts included slavery and selling humans to the Collectors, all in the name of a quick buck.
Eventually, Zaeed was at last able to track him down on the planet Zorya, and confronted him alongside Commander Shepard, who had earlier recruited Zaeed for their own personal mission. Vido goaded Zaeed into trying to kill him so his men could "put him down like the mad dog he was", only for Zaeed to start a fire. Vido panicked and tried to flee, but the fire slowed his progress, which was precisely what Zaeed was counting on. What happens next depends on the actions of Commander Shepard. A Paragon Shepard will forbid Zaeed from pursuing Vido until after they save the trapped workers while a Renegade Shepard will allow Zaeed to exact his merciless vengeance at the cost of innocent lives. If the former is chosen, Vido escapes, taunting Zaeed as he does. Enraged, Zaeed will shoot at the escaping vehicle, one of his bullets killing the mercenary sitting right next to Vido and leaving him utterly terrified with how close he came to death anyway.