Optimus Prime was the leader of the Autobots during the Great War, and currently leads a contingent of Cybertronians on Earth trying to usher humanity into the cosmic community. However, his actions on the planet have brought him into conflict with a number of organizations and individuals, both human and otherwise.
After repeated Decepticon attacks on Earth, Optimus Prime saw fit to annex the planet into the Cybertronian Council of Worlds so as to save it from conquest by Galvatron. While he found support among his own people due to raising Metrotitan, the humans, particularly G.I. Joe were convinced Optimus Prime was trying to subjugate the Earth.
When a massive deposit of Ore-13 exploded beneath Mount Olympus, G.I. Joe took this as an excuse to wage war on Optimus, who was more worried if Autobot City was in greater danger (due to them being atop a larger deposit of Ore-13). When Arcee and Jazz contacted Optimus for reinforcements, he teleported to Portland, Oregon to find the two engaging G.I. Joe, who tried to kill Optimus only for their weapons to prove ineffective. When Soundwave fired an EMP that shut down all the Joes' weapons, Optimus tried to talk reasonably only to receive a (harmless) blast to the face from an RPG wielded by Beach Head. Before the conversation could progress, another alien showed up and killed four humans. Given the alien's metallic appearance, the Joes assumed it was Cybertronian. Jazz tried to tackle it down but Rock 'n Roll intervened, allowing it to fly off. Deciding the alien took precedence, Optimus ordered his forces to pursue it.
They pursued the alien to the Umpqua National Forest, where Optimus shot in the chest demanding answers for its actions. The aggressive alien responded by turning Prime's weight against him and flipping him over, saying he was hunting Dire Wraiths. Optimus's forces however managed to surround the alien who tried to flee only to expose his flank and allowed for a triple attack ending with Optimus running it over in truck mode. He then aimed his blaster directly at the alien and asked it to elaborate on what it was saying earlier. The alien introduced itself as Rom and was invited back to Autobot City, though Optimus did not fully trust the alien due to the Solstar Order's callous disregard in ending lives. The group retreated to the Ore-13 cache beneath the city to compare notes on the Dire Wraiths' interest in Ore-13 and Windblade's knowledge regarding Micronus Prime and Microspace. Optimus believed their main focus should be on solving the crisis with Ore-13 on Earth given their lack of knowledge on Microspace even as Aileron brought intel supporting that the Ore was disappearing into another universe. While the Cybertronians argued, the nearby spacebridge came online which Rom used to send the Ore-13 into Microspace. Optimus made him see that his desire to defeat the Wraiths was putting an entire universe at risk and the Space Knight relented. Optimus assured him that they all wanted to save the Earth and no one had to shoulder the entire burden.
They soon took note of both Snake Eyes and the Heliopolis with Rom and Windblade deducing the latter were the inhabitants of Micronus's universe. Optimus appealed to Snake Eyes, making him see that M.A.S.K., Baron Karza, and the Dire Wraiths were the real threats to Earth. Almost as soon as Snake Eyes agreed to work with the Autobots, Optimus was forced to lead the last defence of the Ore-13 and the spacebridge against an army of Dire Wraiths and M.A.S.K. forces. During the battle, he totalled M.A.S.K.'s Rhino vehicle with his left hand before a group of Wraiths began swarming him. The Wraiths then abandoned him in favour of putting Miles Mayhem in his place before the spacebridge opened revealing Baron Karza, who Enerchanged with the Wraiths, becoming a towering fusion of Wraith, Microspace, and Cybertronian power.
When the Baron began using Wraith magic to funnel Ore-13 into Microspace, Optimus pieced everything together and tried to rally everyone to fight together to fight their true enemy but the organics were more interested in fighting one another. Optimus then grabbed Rom, Snake Eyes, and Acroyear and transformed, trapping them in his cab as he explained the situation and charged Karza an act that convinced Matt Trakker and the recently arrived G.I. Joe of his intentions. Optimus led the attack on the Baron but even with reinforcements, the Microspace tyrant overpowered them until Soundwave hit on the plan to stop their foe and save Earth by forcing him back through the spacebridge into Microspace. Optimus then roused Metrotitan to carry the defenders of Earth to safety only to have his chest ripped open in a desperate escape attempt by Karza where he was saved by an unlikely Miles Mayhem. Once the crisis had passed, Optimus admitted to the humans that he was wrong to claim their world out of the belief only he could defend it inviting them all to work together.
As Rom later flew off, Optimus watched him off and agreed with Soundwave that Rom's trigger happy nature made him extremely untrustworthy but conceded that they had bigger problems that the Wraiths and that Rom would contact them (one way or another) if the Wraiths grew out of control. Beach Head later blamed Optimus for the new status quo that was forced upon G.I. Joe. Optimus's mistrust of Rom was completely reciprocated. As the Space Knight flew, he reflected on Optimus's enormous physical and political power and wondered if the two would one day be enemies but decided to figure it out later. Rom brought up Optimus' claim on Earth to Orphion to try and deter his superior from destroying Earth. It failed.
Months later, Optimus travelled back to Monument Valley to examine a Space Bridge signature and wondered if he'd brought hell to Earth by annexing it. As Jazz and Arcee had a "perfectly friendly debate" about this, Optimus found nothing worthwhile and decided to leave. Just as three Autobots prepared to take their leave, a vengeful Baron Karza appeared wearing Micronus' body and swatted aside the three Autobots.
- Optimus Prime (G1) at the TFWiki