Victory Road has the highest level Pokemon to fight in the wild and there are some trainers in there too but I recommend just trying to beat them over and over again. You'll get good experience and you might end up beating them!
The elite 4's Pokemon the first time you beat it the level range is 40-55. After you beat all the gyms the level range is 50-75.
The elite fours Pokemon are all lvl 50ish so have a good team at about lvl55+ and you should be okay I recommend taking a dark Pokemon because it will be super effective against two of them the elite four are types are, ghost phychic dark and fighting you can fight them in any order you want
There is no sure way to defeat them at all , just have some good level Pokemon , and a range from Ice , Electric , Ghost , Grass , Fire , Ground and normal , and you will win that way
If you don't have any ev trained Pokemon it will be much harder. If you don't you should try getting Pokemon with a wide range of types. Next get moves that have good coverage all around and have good pp. You should look up which kind of Pokemon each of the elite four has. After you have done that and still cant beat them then you should go and level up more. I beat the elite four with my highest Pokemon being at level 53 and my lowest at level 43
All around level 40 range.
Level 78 Pokemon are extremely rare, in fact, it probably is impossible for a wild Pokemon to even get that high. The only way then is to train your Pokemon. When training, try to get a diverse range of types and moves so your team won't be weak to a few moves like having an all weak against fire team or all flying team.
I say that the best way to beat the elite four is knowing your enemy. I know it sounds wierd but if you know what you're up against than you know what you have to do to get better. First, you should train your Pokemon to level 55 or more. I say have at least 2 Pokemon in the 60 level range and at least 2 more Pokemon in between the 55 and 60 range. You need to do this because the champion in the elite four has Pokemon in the 60 range. You also need to get a lot of hp and status healers like max elither and full restores and revives and max revives and etc. I say that you need a strong water type, a strong fire type, a strong air type, a strong ground type, giratina if possible, and a strong Pokemon to back you up for best results against the elite four in Pokemon platinum.
It depends on your Pokemon's level. If it is in the 50-60 range, then train near Indigo Plateau.
There are 5 people, 4 having 5 Pokemon and 1 having 6. The levels of the Pokemon they have range from 51-66. most of the Pokemon are level 51-56.
Jumpluff can be found in the Safari Zone. It can range from the low 30's to the mid 40's in level. That is the only place you can catch one.
Only in Pokemon Blue and Red. For the others, you need some kind of a cheating device to surpass its normal level range.
You can catch Golbat at above that level in Sky Pillar. Its levels will range from 48-56.