Sentinel Prime was one of the Primes, he used to be the leader of the Autobots until the Ark was lost in space, landing on the moon in 1961.
He ends up becoming an antagonist by the end of the third film, when be betrays the Autobots.
Powers and Stats
Tier: High 8-C
Name: Sentinel Prime
Origin: Transformers (Live Action)
Age: At least a thousand of years old (Older than Optimus prime and Megatron)
Classification: Cybertronian, Autobot
Powers and Abilities: Superhuman strength, speed, durability and agility, skilled fighter with blade and shield, contains heavy Cybertronian weaponry including a cosmic rust canon, transformation (Can transform his body into a vehicle)
Attack Potency: Large Building Level (Overpowered Optimus Prime)
Speed: Superhuman (Can keep up with Optimus Prime)
Lifting Strength: Class 5 (Should be able to lift robots of comparable size)
Durability: Large Building level, possibly City Block level (Took attacks from many soldiers and Autobots without much damage, took hits from Optimus prime, and Megatron)
Range: Extended melee range
Standard Equipment: Naturally built in Cybertronian weaponry, double edged blade and shield, the pillars (which can be used to transport armies and even entire worlds)
Intelligence: High; previous leader of the Autobots.
Weaknesses: If he gets hit in the chest right where the spark is he will die.