Treadshot and Ultra Magnus developed an intimate friendship while they were trained by the weapons masters Treble and Gain. They were inseparable. Were, that is, until Ultra Magnus decided to join his brother Optimus Prime's evil Autobot insurgency. Magnus felt betrayed when Treadshot said he could not go down that path, and Treadshot felt equally enraged when he saw what his former friend was capable of. They're a lovely couple.