Both his sons show signs of this themselves. Father brought all the adult villains of the world together and attacked the KND Museum and Moonbase simultaneously, knowing that Sector V would prioritise the Museum on Numbah 1's orders. He also knew ahead of time that the Recommissioning Module was not actually damaged beyond repair, and pre-empted that Numbah 1 would come to their Convention Centre to fetch it — and that he would come alone, without any back-up. Not only that, but he made sure that Numbah 1's "right on schedule" arrival would benefit his Evil Plan — he provided a KND operative's genetic material necessary to make the Module work. As for Numbuh Zero? He distracted Grandfather while Numbuh 1 and his team crashed the Moonbase right on top of him! It didn't kill him, but that wasn't what Numbuh Zero was trying to do — he simply wanted to get him into a Decommissioning Chamber, allowing them to De-Power him once again.
Nightmare Fuel: The senior citizombies' yellow pupiless eyes are quite frightening.
Each of the KND getting infected, but particularly Numbuh 362, considering that she's the strongest member of the KND.
Tear Jerker: Numbuh Zero purposefully broke the Recommissioning Module so that he could finish the most important mission in his life: being a good father to his son, Numbuh One.