Maybe the new villain is a mad scientist. He's creating dangerous biological weapons in a hidden laboratory. His actions are endangering the city's population. The Punisher discovers his lair and has to fight through his army of genetically - enhanced minions to stop him from releasing the weapons.
A corrupt politician could be the new villain. He uses his power and influence to cover up his illegal activities, like embezzling funds meant for the city's development. The Punisher would see through his lies and decide to take him down.
A new villain could be a highly - trained assassin from a foreign land. This assassin has been hired by a powerful underworld figure to take out anyone who gets in their way, including the Punisher. The assassin has unique combat skills and a code of honor that makes him a formidable opponent for the Punisher.