An OC (Original Character) villain in the Justice League universe could be really interesting. For example, let's call our villain 'Shadowcaster'. He has the power to manipulate shadows and create illusions within them. In the fanfiction, he could start by targeting the less - known members of the Justice League, like Hawkman. He'd use his shadow powers to make Hawkman question his own reality, causing chaos within the team as they try to figure out what's wrong with their comrade. This would draw the attention of the big guns like Superman and Batman, who then have to figure out how to combat a villain they've never faced before.
Maybe Orochimaru could be involved with the League of Assassins and become the main villain. He has always been interested in power and dark arts, and the league could provide him with new resources and minions. He could use the league to target Naruto and try to steal his power or the Nine - Tails within him.
Darkseid as a vampire - like being. He could come to Earth and start turning people into his vampire minions. His already formidable powers combined with vampiric abilities would make him a terrifying foe for the Justice League.
First, think about their powers. It should be something unique and challenging for the Justice League. For example, a villain who can control time in a very limited and unpredictable way. Then, consider their backstory. Maybe they were once a scientist who was wronged by the government, which the Justice League is often associated with. Their motivation could be revenge against those in power. Also, give them a distinct look, like a cloak made of energy that swirls around them. This will make them stand out.
According to my understanding, it might be " The Divine College's Opening Sign In to League of Legends ". The protagonist transmigrated to the Divine College world and faced the villain sister, Morgana. The novel is a light novel-derivative doujinshi novel. The main plot is an adventure story in the game world. I hope my answer will be helpful to you.
It could be an evil version of Victor himself. Maybe in an alternate timeline or due to some dark magic, Victor turns bad. His knowledge of the Justice League and his own powers would make him a formidable foe. He could be trying to take over the world or exact revenge on the League for something that happened to him in the past.
Brainiac would be a great choice. He has advanced technology that could be a huge challenge for the OC gamer. The OC might have to use their gaming knowledge to outwit Brainiac's complex systems and plans. For instance, if Brainiac tries to assimilate the world's knowledge, the OC could use their strategic gaming skills to disrupt his data - collecting devices.
Darkseid would be a great main villain. His thirst for power and domination could extend to Trunks' universe as well. He could see Trunks' advanced technology and power as a threat and want to take it for himself. His Omega Beams could be a real challenge for Trunks and the Justice League to counter.
Darkseid would be a great main villain. He's already a powerful and well - known foe in the DC universe. He could be the one who starts collecting the Infinity Stones - like items to gain ultimate power and rule over all universes. His army could also be involved, making it a large - scale war for the Justice League.
It could be Eggman. He might team up with some of the Justice League's villains, like Lex Luthor. Eggman could bring his mechanical creations and knowledge of chaos emeralds, while Luthor provides his strategic mind and resources. Together, they could pose a huge threat to both Sonic and the Justice League.