Dark Energon: Also known as the Blood of Unicron, dark Energon can corrupt a Cybertronian.
Damaged Spark: He is capable of living for centuries, he can still be killed if his spark is damaged. However they can be brought back to life if given a sufficient power of Energon, or revived by the Matrix of Leadership or the AllSpark.
Harsh Environments: Despite the Cybertronians being able to adapt to any environment, they will still completely shut down if the weather is too intense like the cold temperatures from the Arctic circle. They will return to normal if brought back to better climate changes.
Alien Technology
Heavy Artillery Blow
T-Cog Reliance: A T-Cog is a part of Cybertronians' anatomy which allows members of this race to transform into the vehicles of a planet they are visiting. Without it, the Cybertronian can't transorm, are stuck in the mode they are currently in until the T-Cog is inserted back in. Therefore they become more suspectable to attack from either Decepticons or the human enemies.
