Best Transformers Story Arcs

Transformers: Unicron is the IDW culmination of their entire continuity, the planet-eating chaos god finally arriving to end everything in a crossover that forces the entire cast to make impossible choices.

Transformers: Chaos is the climax of the Costa/Roche era IDW run, the Chaos storyline bringing the Decepticon threat to a head in a battle that reshapes the status quo for the entire line.