Are there any games that implemented level scaling in a good way (if that can be done)?
I liked Wizardry 8's take on it. Every zone has a level "band" about 5 levels wide. So the starting zone might be level 1-5, a zone later on could be 8-13, and an endgame zone could be 20-25. The game tries to populate the zone with enemies that match your level, as long as you're within the level band; if you're not, tough. So whatever your level is, there will be zones that give you "fair" encounters, zones that'll kick your ass, and zones that no longer provide a challenge.
There are two more things Wizardry 8 does right with level scaling: first is that it doesn't scale individual enemies, so you don't get level 18 bandits in magical full plate. Higher level encounters mean different monsters, or larger groups. Secondly, it doesn't artificially restrict you by tying your attack rating to your level, like a lot of modern games do to ensure you can't effectively punch above your weight. You can beat higher-level enemies with good tactics, positioning, and preparation, and if you do, you get awesome loot.
Divinity: Original Sin got this last element wrong, by the way. There's no level scaling in that game, which is great, except your hit chance and damage are artificially crippled when going up against higher-level enemies. This system is very strict, too: you can usually kill enemies maybe 2 levels above you, no more. This fucks up the whole open-world conceit, because it doesn't matter how open the world is: you're level 7, so you should go west from the city, because that's where the level 7 mobs are. When you clear out that area, you'll have gained two levels and can go north, to the Dungeon of the Level 9 Mobs (it really is that restrictively designed.)
HERE are the level maps for D:OS, it's a good example of how not to design a game with no level scaling. It feels arbitrary and restrictive, which is a shame because the game otherwise does its best to let you do whatever crazy shit you come up with.