To explain the biomass vs bioelectricity argument Alex eating Cole's biomass would kill Cole, but even a virus needs bio electricity to survive. If Cole ate Alex's electricity it would likely kill Alex even through his regeneration, since no bio electricity means no biological functions and Alex's regeneration is just that. In other words, they both could potentially use this win condition, but Cole had other options on top. Plus, Cole greater power and speed meant he was more likely to get any of them off, including absorption.
Side note, since I forgot. I'm no expert, but this upcoming episode depends heavily on death battle. They already said they are only using G1 Transformers, but unfortunately even the Transformers fan base can't agree on what that means. It might just be the original cartoon, but it also might include IDW comics since they use the same continuity. If IDW is brought in, it sounds even Black Frieza is in trouble. IDW seems to want to give DC a run for their money with insane levels of cosmic BS, and Frieza isn't competing with one of the strongest in that cosmic mess. Of course, if IDW isn't used, then Frieza won't even need to go gold.
