World Evolution or World Domination is a widely used concept in basically every Mega Man series. This serving as the main goal of the main villains of each game, believing that they can change the world a new and better one based on their own beliefs, the most common being that humans are foolish and that the current society is primitive or limited. For this they resort to use force by any means possible and each villain has its eyes set on a different kind of power which would help them on their path, only to ultimatelly fail at the hands of the respective Mega Men.
Since years having working with Dr. Light but never being praised like his former friend, he grew jealous of him and to show the world his genius as a scientist he first modified six Robot Masters which would be defeated by MegaMan along with his last weapon. Since then from time to time he plans new schemes from building and/or corrupting multiple Robot Masters to attempt to take over the world finally being imprisoned and escaping from time to time until he would then work on his final creation, and apparently dying from aging.
Being first the Commander of the Maverick Hunters, later to become corrupted by the Maverick Virus and eventually lead a legion of Mavericks to wage war on humanity, thinking Reploids are superior. For this purpose he would mainly act within the shadows, manipulating others to do his bidding and with this successfully acquiring 8 Maverick Reploids for each game to spread destruction and wreak havoc. From using the X-Hunters, an infected Dr. Doppler to lead Mavericks and build him a Battle Body, plot an attack on the Sky Lagoon so that the Repliforce could be labelled Mavericks and use the Final Weapon, hire Dynamo to unleash a Virus on Earth to mix himself with it and become all-powerful, manipulate the Red Alert and infect its members, up to control the newly made Copy-Chip Reploids (though this orchested by Lumine). Being defeated time after time and coming back due to him being a Virus, he would prove to be a challenge to be only defeated several years after he began his attack on humanity and meet his doom at the Moon where his Virus could not survive to come back.
The first villain of the X series to not be manipulated by Sigma. He was an incredibly brilliant Reploid Scientist, so much that his own companions (including Alia, much to her later regret) turned against him out of mere jealousy. He would then eventually leave to find a piece of the Zero's DNA and work on it, only to become Maverick after being infected by the virus on it, and then would become insane, seeking a World merely for Reploids, for this he would create the deadly Nightmare Virus the powerful High Max along with Zero Nightmare and his revived creations Commander Yammark, Rainy Turtloid, Shield Sheldon, Blizzard Wolfang, Blaze Heatnix, Infinity Mijinion, Metal Shark Player and Ground Scaravich. After a tough battle with him, he would eventually be damaged by Sigma beyond repair, the Maverick Hunters would work on him after defeating Sigma seeking to repair him, his fate remains unknown.
The second villain not being manipulated by Sigma. Director of the Jakob Project and being himself a fully made Copy-Chip Reploid he thought of himself as highly superior as the "old" reploids (term used by him referring to X, Zero and even Axl since he was a prototype) he was successful in outsmarting and even manipulating Sigma in sending eight Mavericks to wreak havoc while working on their plans in the Moon. He would become Maverick on its own, possibly what rendered him immune to Sigma's control. He would then fight the Maverick Hunters himself, only the be defeated.
First a commander who would send the Maverick Hunters to deal with Epsilon and his Rebellion Army, he would travel with X in many missions, acquiring data with his Copy-Chip and blinded with the Power of the Supra Force Metals, he would work behind the schemes to get them and become all powerful while diverting his activities towards Epsilon and his army. Blinded by power he would seek to dominate not only the World but the whole Universe, being the first villain to ever wish for it. He would eventually be defeated by the Maverick Hunters.
Once a scientist which would work along with Ciel's ancestor and find a cure for the "still present" Maverick Virus, he would become unsatisfied with the results obtained after the Mother Elf was created successfully cleaning the virus, he though that Reploids should serve humanity to atone for their sins. So much would be his insanity that he stole Zero's original body, and make him his most deadly creation, the Devil Reploid Omega with him he would modify the Mother Elf into the Dark Elf, with both, being able to start what would be the most violent period within the Mega Man series known as the Elf Wars bringing destruction to 60% of Humanity and 90% of the Reploids. He would then be put in an almost immortal body that would not age and would regenerate itself only to have his past crimes download over time thus he would pay forever for his crimes as well as being expelled from the society. He would then began to work on his revenge, thinking now that humans were foolish he began to apparently manipulate Elpizo to set the Dark Elf free, to later reawaken his deadly Omega, and reconstruct Copy X only for him to serve as a way to become Neo Arcadia's ruler and with it have all the technology for his plans. After Omega is defeated and the Dark Elf restored to the Mother Elf, Dr. Weil's rule over Neo Arcadia would become so ruthless that people would start to escape and with it he began to plot Ragnarok, a way to destroy environment and with it force people to live in Neo Arcadia, for it he would use a reploid named Craft as his new commander along with the eight Einherjars. He would then finish his Ragnarok Satellite with a very powerful laser cannon for his goals, only for the Ragnarok to be first controlled by Craft to attack him and later die at the hands of Zero, for him to later to confront him after fusing with the Ragnarok's core and obtain a battle body for himself, only to be destroyed along with deadly Satellite but not without becoming the later menace known as Model W this triggering that more people sought his power for their own "evolution".
First a member of the Guardians he would be corrupted by Model W and become manipulated by it, using its powers to spread Maverick Revolts so that he could "save" people with his Slither Inc. forces. All of that so people's fear and despair could be absorbed by Model W and give him power. Thinking that Model W will bring a new world he became insane after manipulation and would sacrifice humans and reploids alike for them to become Cyber Elves and further powering Model W. He would then meet his end at the hands of Vent and Aile.
A former member of the Sage Trinity, he would be the man known as the one who created Model W and plot his Game of Destiny in which chosen Mega Men by Biometals would fight with each other until one remained so that it could become the ruler of the world with absolute power. For this he would send the Reploid siblings Prometheus and Pandora to recruit Mega Men and make them wreak havoc to power the remaining Model Ws only for Albert to gather them into the ultimate Biometal the Ouroboros with its power he would seek to create a new form of life, only to be defeated by what he thought would be his successor (either Ashe or Grey).
After beating MegaMan ZX Advent in hard mode, a secret ending will show that Thomas also seeks for the world to be "reset" little is known about how he plans to do this, but it is assumed that he had some thoughts shared with Albert regarding the creation of "new life". He seems to control the four Mega Men Aeolus, Atlas, Siarnaq and Thetis.