It's not any one plan. It's the general chaos.
Clark and his friends and family no longer have a private life. If they're not being stalked by criminals, they're being ambushed by reporters.
A bunch of others would try to blow up significant buildings (the DP, Clark's apartment, the Kents' house, etc.) as either some sort of revenge or to take away his ability to hide or to try to get him to be Superman more or whatever.
Then there are all the Kryptonite plans. Granting Clark an exclusive interview in a room with a lead box. Positioning snipers with glowing bullets near Clark's known haunts. Ambushing him at odd moments and in unexpected ways.
Then you've got all the people who run up to him or call him at home or at work because they want him to fix some problem or other (some of them real things to worry about, many of them cranks). And the ones who loudly complain when their messages are ignored.
The constant attempts on Lois, Perry, Jimmy, the Kents, etc. Some people trying to kidnap them. Some trying to kill them (for being "traitors," just to get to Clark, out of crazed jealousy, etc.).
Not a moment's peace. Not a moment's privacy. Not a moment when any of them can let their guard down ever again. Some of them (not his true friends, but the ones at the periphary) might even start to blame him for bringing all this down on their heads.
That's if the world in general knows.
If it's a couple of villains who keep things to themselves in order to get the first shot... Depends on the villain. I think you've got most of the bases covered. It's just a question of how complex the scheme will get.
One thing you might want to do is keep Clark from knowing that you know. Start messing with stuff around him. Keep him off-balance, never quite sure what's going on or why. Keep him confused and worried, but not quite expecting anyone to come after him while he's in his civvies. You could also send (mis)information to Clark without him knowing that you expected him to find it.
You could plant false info for him to find, getting him to go after the wrong guys. Like they when Lucky Leon got him to steal those missiles. Get him to do stuff for you without even realizing it, then convince the world that he'd gone rogue.
You could kidnap several people close to him, and keep them all in different places. ("You go after one, I kill the others...") Then it's a question of whether you lure him into a trap or try to get him to do stuff for you first.
Other than that... I don't know. Stashing Kryptonite in unexpected places has been mentioned. Blackmailing him has been done.
Oh... Legal issues. Sue Clark for all the damage Superman's battles and rescues have caused. Go after him as an "illegal alien." Subpeona him for vigilantism. Sue the DP. Go after him for any time he could have illegally used his powers to get ahead. Get together a class action suit of people whose hearing may have been damaged by sonic booms. Bury him in paperwork, bankrupt him, keep him from holding any job, etc. While you're at it, turn public opinion against him. Make him completely ineffectual. Play your cards right, and you could get him legally banned from the country...
Paul
