|Image via Rusting Carcass.|
Umbra, the sentient computer, seems to be the worst of this genuinely disappointing bunch. He leads the villainous SHADOW organization in their attempts to destroy the Orbots without displaying a single ability.
|Image via Arioch's Well of Souls|
It's only in the final episode of the series that we see Umbra do something for himself. The Orbots decide to attack Umbra directly (not very common among cartoon heroes, so that earns the show a couple points) and invade the Shadow Star. Which proves to be a colossal mistake because the Orbots and their commander are immediately captured. Umbra swarms them with his Shadowbots, summons the Destructitron, and captures both the heroes in containment fields. The Orbots escape but get trapped in Umbra's memory banks, where the super-computer forces them into a "separate reality" within his mind. That would be an incredible ability - if he wasn't stopped by the Orbot commander banging on a random control panel. After escaping again, the Orbots reverse the flow of Umbra's Sun Smasher weapon and destroy the Shadow Star. Umbra swears revenge before dissipating into energy. Just like Hun-Dred at the end of the similarly short Robo Force, Umbra was destroyed in the last minute.
Let's rate this guy. Coolness - 3. There's not much Umbra has going for him and the stuff he does is kinda superficial. He's got a clever name (the umbra is the center and darkest part of a shadow), a decent look, and an imposing voice (the same guy provided Shedder's voice in a last seasons of TMNT). He doesn't display much a personality, which is to be expected from a computer, but not expected of a cartoon villain.
Effectiveness - 1. Besides the last episode, Umbra shows no ability to accomplish anything. He relies completely on other bad guys to not only follow-through with his plans, but to implement them as well. If Umbra was producing some of the weapons in the Shadow Fortress, it's not obvious in the show, and since he can't even turn them on on his own, I doubt he made any of them. Even in the last episode, when he's fighting the Orbots directly, he only shows snippets of competency and is defeated by the simplest of means.
Overall, Umbra is overshadowed by his peers.