The Serum Amplifies Everything That Inside But it didn’t change Steve Rogers (Captain America) – Dr. Erskine’s
The serum amplified Walker’s horrible qualities. The two Captain Americas aren’t exactly the same, however. John Walker’s poor emotional control and lack of restraint mean that he doesn’t instinctively pull his punches in order to prevent serious harm, and likely isn’t afraid to play dirty in order to win a fight. Steve Rogers, meanwhile, has greater strength of character, making him worthy to wield Mjolnir in Avengers: Endgame.
He’s less hampered by his own ego than John is, which makes him a stronger leader capable of inspiring loyalty and determination among his allies. And in the hearts of MCU fans, John Walker will never be able to live up to Steve Rogers’ legacy.
John Walker killing a Flag-Smasher with the shield is the first time there has been blood on Captain America’s shield. In the comics, Walker actually kills Professor Power while he’s Captain America, which is one of the few times Cap has killed anyone.
As we can see Steve Rogers is not a perfect soldier but a good-hearted man.