Let's take a look at the first few....the villains called Vartox, Hellgrammite and Reactron!
...along the way triggering Karb-Brak's allergy to super powers, and being turned evil and fighting Superman for a time....
...with Vartox needing Superman's help to escape the plans and survive...
Hellgrammite then briefly fought Green Arrow and Black Canary in World's Finest Comics #248 and #249 (mostly 1978) in an odd pair of stories that will get coverage later (mostly because they also dealt with Green Arrow dressing as Batman....).
...which he continued to do in Action Comics #674 (February, 1992, by Roger Stern and Bob McLeod).
...explained a bit in Secret Origins Annual #1 of 1987), and fights the Doom Patrol in Doom Patrol #10 and #11 (July and August, 1988 by Paul Kupperberg and Erik Larsen; and oddly guesting Superman and the matrix Supergirl as Lana Lang in the first issue, with Superman and the Doom Patrol going to face Metallo in Superman #20 of August, 1988), with Larry Trainor trying to use Reactron to get the Negative Being back from Negative Woman (with Reactron being assumed to be dead again...and his history being slightly altered, with his name now being Benjamin Martin Krull).
Deadshot, the second Killer Frost and Blackstarr..
...with Reactron being shot to end his association with the Suicide Squad!
Metallo, and getting a new power source, that of a variation of Gold Kryptonite, that only removes Kryptonians' powers for 15 seconds, resolving in Superman: War of the Superman #1 in July, 2010 (and his history being slightly altered, with his name now being Benjamin Martin Krull).
General Zod (and others from the Phantom Zone), who will come to menace Supergirl in the future....