Although he wasn't techically the "villian",
GMK KG takes the top spot for me as the worst, most disappointing adversary. The design and suit was just garbage, one of the few creations I can honestly say that I flatout
*hate*....say whatever you want about Keizer Ghidorah (and believe me, I'm no big fan of the design at all), but at least it *acted* the damn part of being Godzilla's most powerful foe and arch enemy, the way KG should be portayed. Not to mention that the heads/necks just look horrible and extremely fake-looking all around.
SpaceGodzilla probably takes the next spot. Just an uninspired, lazy design influenced by one of those most overrated Godzilla video games of all time.
Destroyer is not far behind....I remember vividly first seeing news and photos of the poster for
GvsDestroyer back in 95 from
Mark's Godzilla Page (remember those days G-fans?
) and thought Destroyer, as depicted in the poster, look very unique, evil, and just flat out cool...then I saw the actual film a year later...what a letdown
Just another fat, immobile heisei beam spewing foe. Likewise, the aggregate destroyers looked cool, but the execution was far inferior compared to similarly operated kaiju like Kumonga/Kamacuras from
30 years prior, and the eye roll-inducing alien ripoff just added insult to injury. Very disappointing overall on what was a very interesting premise (i.e. a foe connected to the oxygen destroyer).
Fire Rodan as well was a pretty pathetic interpretation of Rodan...like GMK Ghidorah, he wasn't technically a "villian", but as a adversary, I remember how disappointed I was when first seeing it on film (and this was back in the mid-90s when I thought the heisei films were "da bomb!").
After that...hmmm....I suppose
Monster X would have to be up there, as he was barely in the film before transforming. Interesting design, but otherwise forgettable.
After those I listed above, Megaguirus, Orga,
GFW Hedorah, the flying male MUTO, and TOHO Kong get honorable mention....