Sonic 2-Chemical Plant Zone Act 2: Good lord, I could not get past this stage when I was a kid, but now it's easier, although very painful. The worst is beating the boss, then falling into the poison pit after you beat him. Drowning in poison sounds more fun than it actually is...
Sonic 3-Carnival Zone Act 2: When I was younger this level brought me to a screeching halt, because of the barrel of doom. When you reach this barrel you have to jump up and down to get past it, and getting past it takes forever. I remember the first time playing it, the clock ran out, which scared me for no apparent reason. I figured out how to beat the level, but it's still a pain in the ass.
Donkey Kong Country 2-Klobber Karnage: I mentioned this in the "most difficult beaten game" thread, but I'll mention it here again. I hate this level more than Animal Antics. It takes timing and practice to beat this hellhole, and adjusting your aims inside barrels and avoiding enemies and spikes makes it even worse. I swear, I believe I lost 25 lives before I finally beat the level.
Donkey Kong Country 3-Rocket Rush (Game Boy Advance Version): Rareware and Nintendo Punk'd me on this version of the level, having bees being able to kill me in two hits, and taking away the checkpoint barrel in the middle of the stage. So if you die, no matter where you are, you start from the beginning of the level. It's the worst level I've ever played in the original DKC trilogy ever.
Star Fox 64-Venom (Arriving from Area 6)/Zoness: Oh sure, it's a breeze when you're coming from Boise, but when you want to take the hard path, they're not kidding when it's hard (that's what she said, sorry couldn't resist). This level is so difficult, I haven't made it past the beginning where I'm fighting Star Wolf. That's how difficult it is. Zoness is another nominee, since I can not beat the boss for the life of me. And for some reason the game always freezes when I'm in this level.
Legend of Zelda: Ocarina of Time-Water Temple: Yep. Wrong key, wrong door, constantly elevating the water levels, Dark Link, switching from regular boots to iron boots, need I say more? The only reason I beat this level in a day was because I used an online FAQ.
Those are a few of my examples, I'll have more on the way. Thoughts?
Street Fighter IV: Seth:- just really cheap as great as the game is the unbalanced nature keeps it from being as good as the Street Fighter 2 games (although I haven't played Super Street Fighter IV yet, so maybe they balanced it up better there).
Agreed on Rocket Rush, I never found Chemical Plant all that difficult though. Carnival Night Zone act 2 was a bit long, but not too bad.
I did not care for Altitude Limit in Sonic Rush Adventure though, WAAAAAYYYYYY too easy to die there.
One level that comes to mind is the "Road to Nowhere" in the first Crash Bandicoot game (PS1). The whole level was pretty much a bridge in the fog. Not only were most of the planks missing, but many would collapse as soon as you landed on them. To complete the stage you needed to first memorize the whole thing and then execute a long series of jumps with pinpoint precision. I hated it.
Other boring/maddening/poorly designed stages would include:
1. DKC2- Any of the rosy/thorn stages, with all the spikes, spinning barrels, instant deaths galore. I lost a ton of lives on that stage... That game literally took several weeks to beat.
2. Super Mario 3D land- the boss rush stages with the purple mario chasing you. Not hard, but extremely annoying to have to play those castles again with a timer. More disappointment really.
3. Popful Mail: 3rd stage, with all the canyons, mazes of canyons that made navigating through this stage a complete nightmare.
4. Ghoul's N Ghosts- the last stage, so maddening with all the bosses coming back for more. I absolutely despised this level and have yet to finish it.
Always hated the mine cart carnage level in Donkey Kong Country but going back I don't find it nearly as sadistic as I did as a kid.
"Hey, I enjoy escort missions and swimming in a 3D environment where I have to hit things" said nobody, ever.