Just going through it - You're having trouble navigating the maze of rooms & hallways.
Not really a problem when you're like, what, level 80? On a related note, I don't **** around with Zero Isle. The rewards just ain't worth the headache.
Fighting other guys - self-explanatory
What part of "level 80" don't you understand?
The trap-infested rooms - Those are the rooms that have you finding traps left & right, & in a row.
Not a problem unless for some reason you keep stepping on Sludge Traps and you lose all your Apples and you're not even halfway through the goddamn dungeon.
Monster houses - self-explanatory
Once upon a midnight dreary (yeah, that's right, I quouted Edgar Allen Poe. Bow before me, for I am smart and you are dumb!), those were the bane of my existance as an explorer. Now, it's just a Reviver Seed down the drain. And my Electivire's Discharge doesn't really help matters unless everyone gets hit, which of course, never happens. Besides, the guide taught me everything I need to know to survive in those, and I never go anywhere without a few Foe-Hold Orbs.
The boss fights - also self-explanatory
Done with those except for some of the Seven Treasures bosses, which I can deal with easily. Still, I never want to fight Giratina again.
The gang fights - Those are the boss fights that have you fighting an entire squad of people.
Won't have to deal with that until I get the patience to try and recruit the Regis. Remind me to train my male Burmy so it evolves into a Mothim and learns Silver Wind. Come to think of it, I should really blow some Doom Seeds on my Combusken and up its stats so I won't have any more qualms about evolving it.
Honestly, I've really progressed to the level where none of that is even really a factor. But if I had to choose, I'd say the gang fights, since the first time I played, I chickened out of the Dusknoir fight due to concerns about my levels. I mean, I know how RPG mechanics work, but I felt like I had come too far to turn back. That's when I began my practice of grinding my way through dungeons.