I know this is not new information, but I've seen a fresh wave of people confused about what the fuck Andrew planned to do as a 5'0 man with a knife against the literal mafia, so.
I think the fact that neither Neil nor Kevin lost their faith in Andrew’s ability to protect them after he was attacked by Drake (unable to stand his ground against a single man with a bottle, let alone the Yakuza/Nathan with their guns) is the best proof we have that the deal was never about physical protection. This is confirmed by the way Neil never expects Andrew to save him from his father, in fact cuts him loose before Baltimore as soon as danger is truly near.
Andrew is a pretty self-aware character, and he wouldn't make promises he knows he can't possibly see through, so I think he knows what Kevin and Neil also know: what they need from him, and thus what he promises, is not physical protection.
To Kevin, he promises safety from the Moriyamas, and the way we see him enact that safety (at Kathy's show, at the banquet) shows exactly what it's about: when Riko starts getting into your head, when he makes you doubt yourself, makes you think maybe you should go back to Evermore, I won't let you. I will get you away from him, I will treat him like he's just some dude to remind you that you can face him without kneeling. I will be your spine until you find your own, I will stand my ground for you until you can do it yourself.
That's why the scene when Kevin gets to the dorm with his tattoo and Andrew's eyes show so much feeling is huge not just for Kevin but for Andrew: because that was the whole point of their deal, Kevin has found his spine, Andrew bought him the space and time to do it.
To Neil, he promises safety from the people hunting him down, and that means: I will give you something to build a life around (keys, drives to nightly exy practices, someone to lean on, someone who will listen without flinching). When you feel like running, I will be someone you can call to come pick you up. When you forget, I will remind you who you are: Neil Abram Josten.
Andrew stands between Kevin and Riko and between Neil and his father not as an impenetrable wall but as an obstacle in their vision: not shield but focal point.
(Makes me think of that scene in The Haunting of Hill House, Hugh holding Steven's neck to keep him from looking at the ghosts, saying, Look at me, just look at me, keep your eyes on me. That's what Andrew’s constantly doing --even literally, when Kevin is spiralling after Wymack tells the team about the district change and Andrew makes him look away from his broken hand and up at him).
