1) Gandhi: I recently tried a Duel map with him, and even there his UA limited how quickly I could get my last two cities, which were cities #3 and #4 (I was playing Emperor, however; a lower difficulty might be better for Gandhi, but still...)
2) Oda Nobunaga: Not the worst when I can get a good amount of iron without too much trouble. But nothing says rage like only having 4 iron and having had to ally a CS or trade for half that measly amount.
3) Theodora: Very good at King on down, or on Duels (where you are guarenteed a religion can be founded by you), but rage-inducing when on Emperor and up where you maybe build 3 shrines, get a pantheon that doesn't increase faith because you have nothing to use faith-increasing pantheons on, and don't even found a religion. Beyond that, the Dromon is not exactly great unless playing at a slower speed than standard, and the cataphract is respectable but nothing more than a little above average (mounted units getting defensive bonuses is occasionally handy, though.
4) Ramses II: As GreenRoomGames said above me, their UA is not very good on Immortal or Deity. Depending on your terrain, even Emperor games may not be easy for hard-building wonders. The UB is good, the UU is decent (again, nothing great unless playing epic or slower), but the UA which is so overpowering on Prince is miserable on Immortal and Deity. Like Theodora, Ramses II has a UA that rocks on lower levels and fails on the upper levels.
5) Nebuchadnezzar: Babylon, once average on vanilla, is pretty miserable on G&K. The quickest UU in the game to be out-teched (Bowmen become Composite Bows in no time), a UB that is little more than a 5% boost on the standard Wall, and a UA that is pretty good in all reality.
Honorable mentions:
Spain - A knight replacement that acts as a scout is not so great unless its a huge map or you have no place to build a navy. Tercios are pretty good units, and are a reasonable unit even to rush to in some situations. But the UA is so hit-and-miss as to be like going into games blindfolded. Maybe I'll get 1200 gold in the early game this time. Maybe next time I'll get 300 gold all game until I research Satellites, when I'll get another 200 after things are pretty much decided.
Arabia - UA is alright, though double oil is a pretty late bonus. UU is basically a more powerful, slower Keshik that can only hit and run in completely open terrain. The UB, though, is either extremely potent (start location has 3 different luxes in it, and 2 other different luxes occur not too far away) or comically bad (start location has 2 different luxes in it, and the same 2 luxes not too far away; nothing like 14 Cotton and 14 Wine to really limit who you can trade with in the early game, when you only can see the three other civs on your continent).