By the end of the game I want to feel uber-powerful. You can compensate by throwing in more enemies, which makes the player feel like a badass as they mow down individual baddies that were once a threat on their own, while still retaining a challenge through force of numbers.

I play games to get as far from real life as possible. ;)

That's why there's multiple playthroughs/characters. Many games do this and I'm fine with it.

Just buy the ingame money with real money..

https://store.sonyentertainmentnetwork.com/#!/nl-nl/300000-gald-%28nr-3%29/cid=EP0700-BLES01815_00-Q002Z00000000000

Agree with this, all games where you can max out everything become incredibly dull after a while since you'll be crazy overpowered. I like games to be challenging; if you're a master at everything, there will be no challenge. In my opinion; games do this all too rarely today since they assume that this is what gamers want and when you increase the difficulty, the AI beats you by cheating and taking cheap-shots rather than by proper strategy and actual depth of thought.

Elder Scrolls III Morrowind. You could be the most overpowered I have ever seen in a game and it's still challenging for the most part or wouldn't get boring after maxing out everything. it was really difficult to do that. I wouldn't do every OP thing that i could though. I really wish games would let a character become really OP if they were clever or creative but make bosses or certain enemies just as OP. Her hands were pretty feisty. There was this cave, full of bandits that had paralyzing weapons. 

I've finished Morrowind about 5-6 times and after the first couple of times I had to set ground rules to avoid getting overpowered. No stealing glass and other expensive stuff, no Boots of Blinding Speed and Savior's Hide and no enchanting weapons with all damage bonuses. You could practically one-shot every monster besides the final boss with a good katana with all elemental damage. The STR enchantment was also overpowered and I usually had 300-400 STR, this paired with the 300 SP due to the boots and other ehancements and a killer weapon made the game a cakewalk regardless of the choices you made. I don't know how you can see Morrowind as challenging on its own but there are mods that help a great deal.

Oblivion was even worse; my first proper playthrough with the expansion saw me end the game with a character that had 105% damage reflection and 80% magic resist and/or absorb; he was literally immortal and didn't even need a weapon.

Skyrim has super-overpowered archery and stealth mechanics and the perk system is grossly overpowered as well. Bethesda just don't seem to know how to make a truly challenging RPG (yes, I have played Fallout 3 as well and Daggerfall was even less balanced than the later additions to TES series).

The Baldur's Gate games, Icewind Dale, even Neverwinter Nights I and II; now there are some RPG's that offer a proper challenge.

It depends on how it works. pokoko makes a good point that if its implemented poorly, ability to max everything out could make you overpowered.

The way Monster Hunter does it, you can specialize in *everything*, but it would take an insane amount of work, and you can only have one set of armor and weapons active at a time. If you had to "switch" between active skill trees, and could only do so outside battle, it's less OP than just becoming a functional god.

Final Fantasy X and XII had systems where you could max out and become super powerful but it took 150-200 hours or more to achieve and even then you could get your ass kicked (Dark Aeons and cusom monsters in FFX were deadly even near max level), I feel worse about games that make you OP already near the midpoint and with nothing but the basic gear and encounters along the story and a few side missions (Elder Scrolls games have a tendency towards this).

My pet peeve comes when this game in question that forces you to specialize one single way does NOT have New Game +, and hence, I'll never be able to set my character with the whole skill tree.

I don't see the problem in not being able to unlock everything on the first walkthrough otherwise, though.