Diana was almost too compassionate for her own good. In a familiar analogy, she was at one point being assaulted with a number of distracting side quests.
I should help those people with their horses! Not now, Diana.
I should help that soldier who is in pain! Not now, Diana.
I should help those people who lost their village! Not now, D... Where are you going?
Patty Jenkins did a great job building up to that moment, too. The scenes in London, some played for that fish out of water trope (tropes aren't inherently bad). Small diversions, slights against what Diana believed to be right and true tried to chip away at her code.
In games we have the luxury (and often times, actually lack the flexibility) to have an unbendable code. Where nothing much bad happens if we're unwaveringly righteous, and not terrible consequences when we're unrepentantly evil.
I appreciate the softer touch they gave Ares here. In other WW media, he actually inspires and influences violence in those around him. I like that here he says he gives them ideas, but the doing of the malice is still humanity's choice.
Minor spoilers here:
I am a touch sad that Diana had to go Amazon berzerker before she realized that mortals weren't like the stories said; not true good or evil but capable of both. But at least it was against soldiers who were trying to kill her and her allies.
That alone sets her ahead of this universe's Man of Steel, and way out in front of Earth is for Humans Batman.