Creatures of this type will tend less towards beautiful and graceful and more towards quickly reproducing, hard to eradicate, and dangerous to encounter. Works that attempt a more realistic approach may substitute individual ultimate powers for a more "ultimate species" approach hive aliens are often given this treatment, or have attaining this state through successive evolution as a goal. This is frequently lampshaded as well everyone imagines the Ultimate Lifeform to be infinitely beautiful and attractive, and while it may in fact be "perfect" it got that way from so many Power-Upgrading Deformations that it's become an Eldritch Abomination by dint of ugliness. There is an incredibly high chance that their appearance looks human(ish) sometimes the transformation to this ultimate form will make them look human even if they previously lost their humanity along the way or were never human to begin with. Just because someone believes himself or herself perfect doesn't mean they actually are.
The concept is most often subverted by having the being turn out not to be really perfect or invincible, or turning against its creators (especially if it's a villain in the story).