In my opinion Parasite is the most notorious DC villan, why? If you have a villan that can STEAL powers from superheros, then supes would have been pooped by now. Tell me in the comments who do you think is the worst (most evil) supervillan.
I’d preferably go with Detective Comics just because it’s the original comic book business. Jerry Seigel and Joe Shuster made Action Comics #1 in 1939, featuring Superman. DC has a more wider table of characters than Marvel, it’s video games are better (ever played DC Universe Online?), and the villans are more villan-y. That’s MY opinion, but whatever floats your boat.