Here’s a few ways based off the reason you became a villain:
“A corporation killed my father. I will bring down the capitalist system.”
- The Anti-Villian: While not an inherent villain, your family suffered due to greed and corruption and you will stop at nothing to ensure that never happens again. The only problem is that many others are connected to this system and will do what it takes to keep you from achieving your goal.
Your endgame is to completely destroy the current system of governance, choosing either to install a newer, more fair one, or letting someone else fill the vacuum.
Examples would include killing all wealthy business tycoons, working together with heroes to stop bad things that corrupt corporations do, as well as forcing the government to abolish capitalism entirely.
“My father was gunned down by the police.”
- Dark Avenger: The inverse of a “vigilante”, you seek out specifically to take revenge on all those that “abuse” authority. Be it from random cops, to superheroes, to even political leaders, you’ll kill them all.
Your endgame is to show the world that the authority figures are nothing but certified killers and that you won’t stand for it, killing anyone that stands in your way.
Examples of this would include, either solo or as part of a gang, seeking and destroying any police you come across. Eventually, you would seek heroes and would kill them as well. Finally, you would find and destroy elected officials as they essentially fill that same role.
“There are so many people I hold a grudge against. Former bosses, teachers… they’ll come to fear my name!”
- World Burner: You and fueled and focus solely on one thing, and one thing only. Revenge. First it was on the people that wronged you, then it was those that stood by. Eventually it has become revenge on a society that allows such a world. You kill without hesitation or remorse.
Your endgame is to destroy anyone and everyone, regardless of who they are. To you, they are all guilty of making you suffer and should be punished as such.
Examples would include progressively moving from those specifically that hurt you, all the way to trying to kill cities and countries.
“I was bullied throughout my life by different people. The whole society will pay for that!”
- Hero Killer: You focus on taking your anger and frustration out on others to prove you are better. While this started out as taking advantage of weaker normal people, you now get sole enjoyment from defeating superheroes.
Your endgame is to be regarded as the greatest super powered person alive and have no qualms killing to see it done.
Examples would include specifically targeting civilian locations to force heroes to save you, making a name for yourself by killing all super beings, good or bad, or creating a tournament challenging all the supers, swearing to destroy millions if you win.
“I just love money. The more, the better.”
- Tycoon: You focus on acquiring, essentially, all the money in the world no matter what it takes. To do so, you will rob banks, casinos, and even other wealthy people. You are even open to selling your services to other countries for wealth.
Your endgame is to become the richest person in the world by whatever means you have.
Examples would be to become a mercenary/assassin for other villains and countries, robbing banks and casinos, or establishing a criminal underworld.
“I’m in this for power. The world will eventually bend to my will!”
- The New King: You focus on collecting the meteorite stones, similar to what SA was doing. From there, you will either create your own super powered underlings or make yourself a literal god, before establishing a new world, killing anyone that opposes you.
Your endgame would be to cultivate and exert your power on anyone you go up against until you’ve taken over the world.
Examples would be gathering all the meteorites to get stronger as well as multiple powers, creating an army of superpowered subjects, or having an all encompassing criminal underworld where you are the defacto leader.
“The world is chaotic. I’ll bring peace and prosperity, by governing it.”
- The Emperor: You focus specifically on accumulating either literal or political power so that you will become the ruler of the world. From there, you can either truly seek to bring order to the world, creating a Nazi-esque regime, or as an excuse to be a regular overlord that sits on the seat of power.
Your endgame would be to take unilateral control over the world by toppling all major governments and installing yourself as the supreme leader.
Different examples would be recruiting various villains and heroes to work on your behalf, leveraging your [career] to climb the ranks before getting into the political sector, outright acquiring an army to topple the US and existing governments, or manipulating the common people to rally behind you and pressuring the world leaders to give you power.
“My powers allow me to be free. I do whatever I want.”
- Agent of chaos: You focus on getting more powerful and living your life. You have the option to kill anyone or take anything you want but essentially keep to yourself. Your biggest issue is that all the other governments and superheroes don’t like your autonomy and try to either recruit, detain, or kill you.
This villain end game could be killing all the superheroes and making it clear to [the President] that you will do whatever you want and won’t be bothered anymore.
Different game examples could be “collecting” romance options to make a harem, becoming a millionaire (+) with the nicest home(s), expanding your powers even by testing them on people, or all of the above.
This is just a general consideration for how to implement character motivations into their actions while being a villain.