Gavin O'Connor's well-received Warrior is once more permeating the entertainment industry following news that the director is kickstarting a TV series that serves as a spiritual successor to the 2011 mixed martial arts flick. It's welcome news for MMA fans who, while it was a niche genre, loved it for being a modern Rocky as Tom Hardy's Tommy had to fight his brother, Brendan (Joel Edgerton), to see who'd win the Sparta tournament. The victory ultimately went to Brendan but while it seemed like he outfoxed his brother in the octagon, there's more to Tommy tapping rather than passing out to end the fight.
In Warrior, Tommy hated Brendan for leaving him with a drunk dad in Paddy Conlon (Nick Nolte). Brendan departed to start a family, leaving Tommy to take care of their dying mom in addition to enduring abuse from their dad. It's why Tommy's rage had him decimating everyone in the tournament, as he wanted to win money to offer up to the widow of someone he served with in Iraq.
But in the final fight, Tommy had an injured shoulder, and the dislocation severely hurt his chances. Brendan didn't want to continue but the brawl went on and Tommy submitted to a choke. However, it's worth noting that only when Brendan told him, "I love you!" did Tommy tap, which ties into their turbulent relationship.
Throughout Warrior, Brendan made repeated attempts to mend fences, reminding Tommy that he needed his own life and couldn't be blamed for being a father and school teacher. Tommy, though, had all these demons to live with, ergo why he never offered forgiveness. He was even more bitter that he had to resort to Paddy training him again, reminding him of everything and everyone he hated. But in time, he began to understand Paddy's angst and pain over watching his wife rot away, and bit by bit, he started to see what Brendan was fighting for: money to save his own wife and kid from mounting debt.
Granted, Tommy couldn't relinquish his own quest for funds, as the government seriously mistreated his friend's wife, but he saw that Brendan, like Paddy, was a flawed man who did try to do right in the world. Unfortunately, that didn't mean either one did right by him, but Tommy began losing his anger and gaining empathy by being in closer proximity to them. Using Paddy out of necessity gave Tommy the insight he needed, as he could tell Brendan didn't want to fail at being a caring, nurturing provider the way their dad did.
This is why Tommy tapped at the end of Warrior, as it was his way of accepting Brendan's apology and forgiving him. It's known in the tournament that Tommy doesn't quit and is someone whose ego would quicker let him go unconscious rather than giving someone this pleasure and ultimate power over him. But in this case, Tommy remembered what family stood for, and placing Brendan first was part of the healing process.
He knew it'd land him a court-martial with the regiment waiting to arrest him for going MIA, but still, Tommy didn't feel like a failure despite not grabbing his purse. After all, there was no price he could put on patching it up with the brother who helped take care of him growing up. That tap was his way of giving back and creating a path to reconciliation, as he also knew it'd damage Brendan if he finished Tommy by making him pass out, which ultimately proved to be taps of mercy for the brothers.