"Let our polluting powers combine!"
"By your polluting powers combined, I am Captain Pollution! Ha! Ha! Ha! Ha! Ha! Ha!"
- – Captain Planet, Mission to Save Earth Part I
A Blighter is to a Druid what a Blackguard is to a Paladin. Turning the whole “Revere Nature” thing on its head, Blighter seeks to actively destroy nature nature for its own sake rather than for civilization or whatnot. Yes, it’s an entire (Prestige/Variant) Class dedicated to being a Captain Planet villain! Compared to fiendishly empowered champions of evil, hating nature for the sake of hating nature (not even ripping nature apart for power) is a fairly lame concept that renders Blighters less popular than the other bad-guy only class and, as a result, means they don't appear nearly as often.
In 3rd Edition Dungeons and Dragons, Blighter is a Prestige Class from Complete Divine and notorious for being one of, if not the, worst in the system. Qualifying requires the user be a 5th level ex-Druid, plus any method of gaining an extra point of BAB (Yes, it is a non-martial class with a meaningful BAB requirement). While Blackguard gained effective levels for all ex-Paladin levels its user had, for a Blighter these five/six levels do absolutely nothing racial HD doesn’t do. What does a Blighter get for this? Spellcasting from the unique Blighter spell list, which is just a heavily gimped Druid list when Druid was already the worst core caster, a variant wildshape, which is behind the wildshape you’d have if you remained a Druid, a crappy blast (Su), and not needing to eat or drink (which is useful but acomplished by a cheap magic item that also lowers your sleep needs). Blighter spellcasting is technically accelerated, but the six dead levels needed to enter mean you’ll only break even in terms of spell levels at level 12 and don’t come ahead till level 14. Perhaps the most pathetic part of the class is that Blighters need to destroy nature to prepare their spells, so if they actually accomplish their goal of destroying all nature, they lose all their power! The class is so bad that most fans of Red Hand of Doom strongly recommend either a total rebuild of the Blighter side-villain, or rewriting him to be cursed to his current state since he hardly lives up to the supposed instant death he’s described as (especially so if the PCs remember the staff of healing they got early on in the module, and what Heal does to undead).
Pathfinder's Advanced Player’s Guide introduces "Blight Druid" as a Druid archetype. This archetype covers, rather than the anti-nature for its own sake crazies that Blighter did, Druids that embrace natural decay ("ENTROPY HAS UNMADE THEM"). This version is actually pretty fine, mostly because, aside from the Druid archetype standard (that is likely why you’re taking the archetype) of requiring you pick from a different list of domains, it only changes secondary features with decent trades.