Unmarked spoilers are ahead, per Spoilers Off rule.
Tom Doss saving Desmond from being court-martialed by presenting a letter from the Brigadier General saying that his religious beliefs are protected by military law.
During the first battle, Ralph gets both of his legs blown off and begs Doss to help him since he has kids back home. Doss manages to provide first-aid and convinces the medical staff to bring him back to the aid station despite them believing it's too late to save him. Ralph winds up surviving.
Smitty and Doss bonding when they're in the foxhole on the ridge together. Of course, this later makes Smitty's death absolutely heartbreaking.
Private Doss' night-long heroic montage of rescuing soldiers wounded and crying out for help. Many of whom once hated him and called him a coward.
So determined is Doss to save them that he's shown several times close to passing out and his hands even start to bleed from lowering the bodies using the rope secured at the edge of the escarpment. But every time he seems close to quitting, he simply prays "Please, Lord. Help me get one more." and keeps going.
During this night long rescue mission, Doss finds fellow soldier, Pinnick, scared for his life, blinded by the dried blood covering his eyes and shooting blindly too. As soon as he calms him down, Doss wipes the blood from his face and tells him to see, Pinnick gives a bright smile saying "I thought I was blind" and joyfully chuckles, with Doss smiling too. Word of God from Doss himself says when this happened, seeing Pinnick smile like that would have been payment enough for his efforts.
Captain Glover and the rest of his men finally coming to accept Doss after his 'miracle', even telling Doss that they won't launch the next assault without him. Doss agrees to join them even though it's on a Saturday and he's not supposed to. Cue the entire company patiently waiting in mutual respect as Doss silently prays for all of them, even though it starts the assault 10 minutes late.
During the final battle, Doss realizes he's lost the Bible Dorothy gave him after he gets hit by a grenade and is being taken off the battlefield. Two members of his squad immediately run back to the area to find it and manage to give it back to him right before Doss is shipped to the hospital.
It's even more awesome and more heartwarming in real life. They don't find the Bible right away. Rather, Desmond's entire company pitched in to comb the area and eventually find it.
Doss patching up a wounded Japanese soldier while in the tunnels, and later lowering two wounded Japanese down the ridge during the night. Despite the wounded being part of the enemy force and all the brutality we've seen from the Imperial Japanese Army, Doss has it within himself to show compassion to any wounded, friend or foe.
