Nuzlocke Difficulty Power Rankings
Contribute with your own stories of problems and difficult parts + advice for future Nuzlockers.
Rankings subject to change.
1. Black & White 2 Challenge Mode
Consistently high difficulty + heightened level curve = no fun. Limited capture areas, especially before Castelia, make team building particularly difficult. You won't have a full team before Roxie and there are very few Pokémon you can access that will help you with the first 3 Gyms. All gyms are given an added Pokémon and the existing Pokémon are generally improved. (See BW2 Normal for further explanation)
Improved version of DP spikes the difficulty significantly. Nearly all plot battles (from Mars' Fat Cat to Cyrus's death squad) are difficult and common 'mon death points. Last 3 rival battles are sudden and difficult. Gyms after 3 have beefy and hard-to-counter teams. Improved E4 has a huge variety of awesome Pokémon and Cynthia packs an even more challenging team. Often considered the hardest Nuzlocke.
3. HeartGold & SoulSilver
Through Lance, HGSS are fairly easy. There are a few sticking points before Indigo (Morty, Jasmine and the Rocket Hideouts come to mind) but the E4 is relatively low leveled and has only so-so teams. Post-E4, however, gives you nine high-level difficult battles without any source of low-risk grinding as well as one of the highest-level and hardest battles in the franchise in Red. Also easily the longest game in the series. If you're only playing to the E4, it's likely the easiest, but if you plan to do the whole game, its sheer length may be your downfall.
3a. Gold, Silver & Crystal
Considering HGSS is nearly identical to Crystal in plot, battles and pretty much everything else that's not graphics, they're roughly the same difficulty. The only major difference is the Kimono Girl battles, which are later and somewhat harder in HGSS.
4. Black & White
Early game is pretty difficult with limited team members and a rather aggressive second Gym. Gyms 3-5 are also fairly difficult and the final Gym can present problems, especially without a good Twist Mountain capture. Also has a limited number of areas where Pokémon are catchable. Final battles are often Nuzlocke enders.
5. Black & White 2 Normal Mode
A lot of the same problems as BW2 Challenge and BW, but without the insane curve on levels and easier early Gym Leaders. Ghetis battle is easier than in BW but Corless battle is fairly difficult and Plasma Ship sections can be tough.
6. Diamond & Pearl
Much easier than Platinum due to a lot of Pokémon omissions that make Gym and E4 teams much easier. Order of the Gyms also allows for mid-game team building and grinding. Story battles are still difficult though teams are slightly less hellish. Cynthia also has a harder team and a harder Garchomp.
Still relatively challenging but the curve doesn't start until after Gym 2. The middle leaders are troublesome and Tate & Liza are very difficult. Though the E4 is probably easier since Wallace is an easier champion than Steven, the increased difficulty of the Gym Leaders and story battles make it somewhat harder. Grinding is also particularly tedious.
8. Ruby & Sapphire
Same issues as Emerald though the Gyms are generally easier overall. E4 is harder because of Steven though only marginally so.
9. Red, Blue & Yellow (and Green)
Breakability of the game increases the ease significantly, though many of the sections may still be challenging (e.g. rival battles, Giovanni fights). After Misty, you can essentially skip directly to Koga if you want, allowing you to gain a lot of EXP fighting trainers and doing Rocket buildings before fighting Gym Leaders. RBY ranks above FRLG only because of difficulty with grinding and the fact that RBY's mechanics are so insane you're more likely to lose Pokémon to hax. The E4 is relatively challenging but many repetitive teams make for easier sweeps. The final battle is also one of the more difficult but it is similar enough to earlier battles that there should be some level of familiarity going in.
10. FireRed & LeafGreen
Somewhat less breakable than RBY but still allows for significant sequence breaking and few major sticking points. Vs. Seeker grinding also eases some of the problems the game has with levels, making it somewhat less stressful. Gen III moves and TMs also make many more Pokémon viable, meaning captures that would be shit in RBY may be better in FRLG.