In the debut trailer, Grimlock's nod to Prime. It's as if he's saying "Don't worry, I've got this."
Just as heartwarming was Optimus carrying an injured Bumblebee, oblivious to the devastation around him, then setting him on the ground and reassuring him before focusing on the battle.
At one point in Cliffjumper's chapter, there's a very nice, quiet scene where he enters a holographic observatory on a gorgeous spiral staircase. In awe, he ascends the stairs and looks at the highlighted planets along the way, particularly prehistoric Earth, and you can hear the admiration in his voice when he relays this to Jazz via radio.
As utterly messed up and enraged as he is, Grimlock tearing apart numerous Decepticons and Insecticons to rescue his teammates, as well as his response when he hears about Sludge, shows that there's a soft spot in the guy.
Soundwave cements his dedication to his leader and his cause with the lingering look he gives Megatron's body, and when he resurrects him. Not to mention his overall relationship with his cassettes.
Also, you can pet Laserbeak as either Soundwave or Megatron. The fact that he tries to bite the latter, who responds with laughter at this, is quite impressive.
Think about this as well: Megatron rarely, if ever, throws any threats or insults towards Soundwave. This more or less shows the trust Megatron has towards Soundwave, making this more heartwarming, maybe since this is Megatron we're talking about here.
In the level where you play as a generic Decepticon, before you play as Starscream after Screamer kills the other generic wait awhile and listen to the Mooks commentary. He says the other mook was his best friend and that they would have made partners next week. This is a DECEPTICON saying someone is their best friend. Also a tearjerker in that after slaughtering them left and right you realize that the Decepticon troopers are in fact not just generic drones.