Unlockable Characters; Improbable/Impossible

Daisy, Mario Kart Wii--Win the 150cc Special Cup, or log 2,850 races.

I figured winning the 150cc Special Cup was the easier route--NOPE!

I lost count of how many tries it took, but I finally won by one point and got Daisy.

 

I Forget How Many Characters I Unlock In Mario Kart Wii When I Was Younger (Which I Broke It Because Of Region Locking...) But I Think The Hardest Characters I Got In Mario Kart Wii Is Maybe Dry Bowser Or Rosalina

Dry Bowser: Mario Kart Wii Is My First Mario Kart Series Game, So I Don't Know What It Takes To Get A Star That Only I Learn That I Need At Least Like 60 Point Or Something Like That To Get A Star. I Had Range From A Star To Three Star Before. It Is Because I Don't Know How Many Point I Need To Get 1 Star That I Keep Racing Again And Again In All Cup And All Grand Prix. And Unknownly, I Actually Unlock Dry Bowser Until The Unlock Screen When I Knew That I Unlock It.

Rosalina: I Don't Know How I Get Her. I Just Played Everything, From Time Trial To Races And Mirror Mode Which I Unlocked It Just A Few Days Before Got Rosalina After Playing A Time Trial On Luigi Circuit After Watching A Credit Again. When I Learnt Just Now That I Must At Least Race 4,950 Time Which Makes Me Feel..."That Is The Hardest Characters I Ever Unlock."

 

The Swordmaster Karla (of Fire Emblem: Blazing Sword). Requires playing on Hector's route (she appears on a Hector-specific side-chapter late-game) and having a lv. 5 Warrior (promoted class) Bartre (who is not the easiest character to use). You find her in the arena on that chapter, and both Karla and Bartre must survive the round for her to be recruited. Thing is, Bartre uses axes, which are weak to swords; however, if Bartre uses a Swordreaver/slayer he could potentially kill her (as the name suggests, it reverses the weakness of the weapon), and even if he doesn't she could crit him to death (as Swordmasters have a very high crit rate). So, your best bet is to give Bartre a bow (which he can use as a Warrior) and equip the Iron Rune (which prevents criticals from triggering); he has enough HP and Defense to survive a couple of hits from her (assuming he hasn't been RNG-screwed). Thing is, you're not going to even know this is a thing your first time playing through Hector's mode... Especially if you didn't think to steal the Iron Rune from Lloyd/Linus earlier.

The result: a subpar swordmaster that somehow manages to be worse than Lyn (who is well-known for getting RNG-screwed in her Strength stat), and with only a couple of chapters to go it's a real let-down. Maybe if she showed up with the stats she has about five or so chapters earlier, and maybe as a level 15 Myrmidon (unpromoted), she'd be a much better unit (though Lyn still has the edge due to the Mani Katti and bows on promotion).

Thankfully they fixed her in Fire Emblem Heroes, so now she's a powerful swordmaster worthy of her title.

 

Artoria Pendragon in FATE Extella. There's nothing to hint at how she unlocks except the ??? Side Missions, and they don't even tell you what they are. I never got her while I had the game, and from what I hear, she's not worth the effort.

Also Model OX in Mega Man ZX. I say Model OX because one of the ways you get it is by defeating Omega Zero AND it also allows you to play as Omega basically.

Then there's the two unlockable characters in Enter the Gungeon. The game is so hard that reaching the end is improbable let alone unlocking even just one of the two characters (I forget their names.) That's all I've got off the top of my head.

 

I've got a new one from personal experience. Just from the sheer ridiculousness of the trouble I am having, Shiny Growlithe in Pokémon Let's Go Pikachu.

So far I've spent five days total on this shiny hunt counting today with absolutely no success. I have even gone through the trouble of getting the Shiny Charm yesterday. I have caught literally hundreds of Growlithe, and this is just the tip of the iceberg.

I have caught so many Growlithe, I have exactly 270 of its candy and even maxed out all of my Mighty Candies at least once each. Those first four days? Not a single Shiny Pokémon to be seen, Growlithe or otherwise. I haven't caught even a fourth as many Pidgey, yet I have seen 3 Shiny Pidgey, including one I caught looking for Beedrill before even getting the charm and the one I caught on the first day playing the game.

Today, the game threw 3 Shiny Pokémon at me, much to my annoyance: Rattata, Porygon, and Jigglypuff in that order. Both of my hands actually hurt from flipping the game off.

Now, I actually have the shiny in question on Pokémon GO, but that one probably isn't going to be anywhere nearly as good as one that you hunt for.

Edit: Something I forgot to mention. I've burned through nearly 20 Max Lures. That is only counting today's Lures, not any of the Lures I used on the other four days I spent shiny hunting Growlithe.