Santiago shows a singular focus, doggedly pursuing his task regardless of pain or circumstances. Shrug Off allows him to remove a Condition that has been applied to him, helping him bypass such effects as Poison and Burning. When he is wounded, his effectiveness actually increases as "¿Es Todo Lo Que Tienes?" kicks in, putting his Sh above even Perdita's skill level and providing a positive twist on damage. Even when Santiago has taken enough damage that he should succumb to his wounds, Hard to Kill keeps him the game, fueling his recklessness. Despite this he is not invulnerable, having fewer Wounds than most other Enforcers and only average defenses.
Although he likes to be in close, Santiago doesn't want to get too close; He is not a close combat expert and his capabilities tail off substantially when he is engaged. Santiago is at his best standing several inches back from the main fray where he can rely on I'll Cover You to fire on enemies his more melee-oriented Family members have engaged, using Companion to activate right after they charge.
Santiago has a few interesting options available for his singular Upgrade slot. Tormenta De Plumo goes well with his placement on the battlefield but doesn't take advantage of his enhanced shooting under "¿Es Todo Lo Que Tienes?". If you want to shore up his survivability, Lead Lined Coat provides him with armour. Alternatively, Plant Evidence can add a silver-lining benefit to Santiago's eventual demise by helping you achieve Scheme Marker objectives.
Probably the best Upgrade for him is Hermanos De Armas which lets him provide his Crew with more mobility, launching close combat allies toward the foe or helping reposition the team. For added efficiency, Hermanos De Armas costs a zero action to use which Santiago would otherwise only use for the situational Shrug Off. This gives him something to do every turn and that works to keep the team together.
Whatever role you give him Santiago approaches it with gusto. Using him in your Crew is a matter of balancing his dual nature. He wants to dive into the fray and rapidly close the gap with the enemy but he needs to hold back and keep at range. He wants to take some fire to unlock his entire potential but he mustn't take too much or he goes down. Bring him to the table and you can feel his urgency and caution as you strive to seek the right balance. Get it right and he can be a game changer.