Going way back for this one, but I think it counts:
To unlock the true ending in NES Double Dragon II, you have to beat it on the hardest difficulty.
Which, in the regular beat-em-up levels, isn't too hard. But if you think the legendarily hard platforming sections are bad on normal difficulty, then prepare to rip your hair out.

 

Batman Arkham Origins: Blackgate - to unlock all Batman costumes, you have to beat the game three times. Maybe not hard, but really tedious for completionists.

 

At least you've (probably) got the invincibility suit on the other two playthrus, but yeah, that's annoying.

I will add any game in which you have to play through some sort of extra "challenge" mode that was tacked onto the game to either complete 100% or unlock some prize. Arkhym City and God of War come to mind. The more recent Lego games have a ton of filler as well. There's no reason I need to fly through another twenty rings for the four hundred and fiftieth gold brick (with traumatic flashbacks to Superman 64).

 

Iirc, I evaded them by going under the stage and luring them into their deaths. Been forever since I did it, though. Nothing like Wii U or brawl where I just used Lucas' up B and get 21 kills....

Speaking of Smash Ultimate, those panels where you have to beat 3 Lv9 NPC in 3 minutes without dying or something. Aka the only panels the game won't let you use the Panel Hammers one....

 

Oh yeah those. I'm unable to accomplish that.

 

I personally wouldn't regard God of War 100% completion as particularly difficult or cumbersome. At least for the first four games (haven't personally gotten around to 3 or the latest, yet...).

Because the games let you tackle the hardest difficulty in New Game+ mode, you pretty much just fly through that final challenge. And the arena modes usually aren't too challenging, because there's usually one totally AI busting combo that's super abusable that you can just spam continuously, or abuse the invincibility frames from grab moves and QTE finishers. Easy Platinum trophies, for me.

 

The Zodiac Spear in Final Fantasy XII requirement is pretty BS: don't open four specific treasure chests scattered around the rest of the world map. You open even one of them, you miss out on the game's best weapon. Naturally, they are in no way marked as unique and at no point does the game tell you about any of this. And if that's not bad enough, Vaan is in the game, too.

 

I think that weirdness is resolved in Zodiac Job System?

 

Star Ocean battle trophies
Have fun Plat-ing Last Hope
Most aren't too bad, then you get 'heal a teammate the exact amount of missing health', 'deal exactly 77,777 with an attack' 'kill an enemy with exact poison damage'

 

Or do like I did and somehow glitch the system on the 'tank' boss and get the maximum number of lives.

This whole post makes me go

It's not the second half of the game. It's one, albeit large, dungeon with multiple bosses. Also, no one unlocked the ending despite game guides still being popular and sold back then? Did no one buy the guide for this game for some reason? Besides, it wasn't even that random. You don't wear a useless accessory but equip something that does something useful, and your loyalty is manipulated by keeping treasures found at the end of dungeons. Why wouldn't you keep some of the really nice items you find for yourself, from a game play perspective.

Like I said, it isn't that hard, aside from sending your boy toy up at a specific time.

Certainly less obscure than SO2's secrets.

 

It's not "half the game", but it is almost the entirety of the "main" story (and IIRC, it's at least two dungeons. There's the final dungeon, yes, but there's also the bonus story area that you run with Arngrim, Lezard, and Mystina). And what you say is sorta the problem. It's set up to sell strategy guides, and is not particularly intuitive on its own.

Yeah, you can maybe stumble upon it on your own, by playing "selfishly", but video gamers are practically conditioned to follow the in-game instructions, and unlocking the True End requires you to defy most of what the game's been telling you, without giving you a reason to suspect ulterior motives. And not even wholly consistent on that front, because again, you have to sacrifice the use of your best character early in the game. While the game sort of nudges you in that direction by making him the most fitting candidate for the chapter's requirements right from the start, there are a couple of other characters that can be made equally suitable candidates with the proper level-ups, thus allowing you to keep your most useful character, instead of giving him away in an action that hasn't been suggested to give any lasting benefits. You tribute your Einherjar to receive your Chapter rewards, and other characters will give you those same rewards.

 

Another bad unlock requirement is basically owning another game to unlock what's in said game.
Examples: in Mario Kart Wii there are multiple requirements to unlock Rosalina. Either do alot of races, or own Super Mario Galaxy.
In the Incredible Hulk video game based on the 2008 movie, to unlock the Hulkbuster costume you have to own the 2008 Iron Man game. So... you're pretty much have to spend more money.

 

I don't dislike them because they're difficult. I dislike them because they have virtually nothing to do with the actual game. It's like playing through Super Mario Bros and then having to play a dozen mini-games from Mario Party to finish the game. None of the games I mentioned need the additional "content" to be great games.

 

Most Warner Bros. and recent EA games have this problem.
It will either cost alot of your time, alot of your patience, or alot of your money. Probably all 3!

 

Almost a decade ago, I wanted to get the trophy for completing the full setlist of the songs available in disc of Rock Band 2 on PS3. Not sure how long it took, might have been 4 hours but I got it but made my throat hurt for 2 days.

I had to drink some tea to help.

It's the only game I ever did that with but I do sing from time to time.

 

SWGOH

 

I'm guessing SW is Star Wars but I don't know of GOH.

 

Star Wars: Galaxy of Heroes.
It's a mobile game by guess who:
EA!

 

Dark Souls 3, Dark Moon Covenant. Have fun with a 1% drop rate.

 

(Holds up a crucifix) Begone EA!!!