Complex sentence: Now, Optimus Prime, Scarlett and the other heroes must unite again to prevent both worlds from warring, and put an end Colton's insane ambition once and for all.
Split into simpler sentences: Now, Optimus Prime, Scarlett and the other heroes must unite again to prevent both worlds from warring. And by the end, they must put end to Colton and his insane ambition once and for all.