Complex sentence: Optimus is the stalwart and brave leader of the Maximals during the "Beast Wars" but his leadership degrades as his fanaticism to defeat Megatron grows he nearly kills the team during a battle against Vehicons in a factory.
Split into simpler sentences: Optimus is the stalwart and brave leader of the Maximals during the "Beast Wars". This is apparent when he nearly gets the team killed during a battle against Vehicons in a factory.