When Mirror!Optimus offers Cliffjumper the opportunity to execute Rumble in the smelting pool. While unwise, Cliffjumper's attempt to talk some sense into Optimus comes across as rather heartwarming, especially from a confessed Decepticon hatter.
Cliffjumper: You know I despise the Cons' more than most but we can't just destroy him like this for entertainment! It goes against everything we stand for, what you stand for. I can't believe I'm the one telling you this! This isn't justice Prime, it's murder! This isn't how we do things! I'm sayin' you need to stop this!
What makes it really good though is the fact that up to that point, Cliffjumper still wasn't a hundred percent sure he trusted these Mirror Universe Decepticons. But after witnessing Megatron putting himself in danger for a stranger (not unlike his Optimus Prime) Cliff is finally convinced which side is in the right.
Despite his overprotective nature, Starscream respecting Sephie's wish to be her own hero.