From the perspective of Bob, the aliens were utterly terrifying. It regretted that it had chosen to attack the aliens right off the bat when they were actually peaceful and good entities with no intention of harm.
Especially when they were so absurdly powerful. When Bob saw Ria effortlessly controlling their flames and wielding them against them to overwhelm them as dominantly as she did, he realized how much of a mistake he had made to antagonize these alien beings.
Another terrifying reality was that one of the aliens managed to learn to speak their language at an alarming rate despite being an alien with an entirely different physiology. The aliens were capable of producing sound, but it was a much lower frequency with much lower density than the means of communication of the macrobes.
