The plot is identical to Super Kids until Thaddeus is about to kill Phineas, and Ferb doesn't notice the fuel rod of Pizzazium Infodionite and Isabella wakes up and tries to slice Thaddeus with a laser but misses and slices off Phineas' arm from the elbow down. Ferb uses his telekenisis to throw Thaddeus away. Ferb build Phineas a robot arm that's just as good. Thaddeus quickly takes over Danville, turning buildings into energy and absorbing them in his energy form. He builds a dome-like web of energy, but when Team Invincible comes, he quickly defeats them, but Ferb uses his powers to beat him up. Thaddeus absorbed too much energy, so his physical body is destroyed and becomes a 5,000 foot tall bemoth composed purely of energy that is invincible (law of conservation of energy).The bemoth destroys most of downtown Danville except for Doofenshmirtz Evil Inc. Baljeet calculates a plan and Ferb builds it. It's a wire that leads to a laser that will launch him into space. Energy bemoth Thaddeus steps on the wire and is being sent to the laser. But it overloads, self-destructs, and Thaddeus, but in regular size energy form, dies happily, after being comforted by Phineas in his last moments. (Note: Thaddeus dies because his powers are fading (the explosion removed all of theirs) and his physical body was destroyed, so he would have no mortal composition once his powers fade.)
"Too Young" Line
Phineas: "You aren't evil. You just took the wrong path."
Thaddeus (dying): "Right."
Phineas: "And all wrong paths intersect with the good one at the end."
Thaddeus (dying): "Yes. Yes they do. Goodbye, friend."
(Thaddeus dies and his energy body fades.)
Officer: 962minez called to conscription!
(962minez tips his hat and walks away.)
Baljeet: "That bemoth is invincible! The law of conservation of energy!"
Ferb: "Which is-"
Baljeet: "Energy cannot be created or destroyed, but can only change form!"
Phineas: "Change form, change form, that's it!"
Baljeet: "I already have the plans in my head."
Isabella (after watching Thaddeus die): "Watcha doin, Phineas?"
Phineas: "I just made a person's last moments a little easier for them."