So, theories regarding the SPOILER in the film?

Just got out of the cinema. 10/10, may bcome top 3 films for me. So in the film, Simon(Mark)'s etes go red. Theories??

1. He finally accepted the "Simon the Butcher" past.

2. Some kind of superpower unlock (cliché, I know)

I lean towards 1, but why show an eye colour change? The scene implied it with his violence towards the creature.