Beast Machines: Transformers

With the others Maximal's sparks taken by Megatron and now having the body of Optimus Primal's "Optimal Optimus" from the third season of Beast Wars, Optimus has to face Megatron alone. Megatron absorbs the sparks and then Optimus pushes him into the planet's organic core, reformating Cybertron and destroying both Optimus and Megatron.