Can anyone tell me gyarados' weakness and some good partners for it?the analysis is confusing.
Also what's the standard set for it?The same with pre aegi ban?
I use a bulky DD standard Gyarados, which is very effective indeed. Sub, DD, Waterfall and, unusually, I use Earthquake in slot 4. This is because opponents will often send in an electric to stop the sweep, and Earthquake after a DD will often OHKO them. Also, I send in Gyarados to counter steel attacks (resists plus intimidate) and Earthquake is good against steels.
Sub + Leftovers is the key to the set. Sub can scout for attacks if you are faster. But its main use is to obliterate stall. The opponent often gives you a free sub with an attempted status, and then often struggles to break it whilst you DD. Sub also stops you being revenged killed. Having the sub up gives you a free hit on the revenger, which can be enough for you to get the 2HKO.
Bulky DD is Adamant with some HP, some speed and some attack -- look it up in the Dex.
I prefer standard Gyarados, because I like to utilise Intimidate plus ground immunity all game. I've used the Mega a lot too and it's also very good though.
Gyarados is an excellent balanced min but it does have a few weaknesses, depending on what moves it runs and whether it is Mega or not. You'll want an answer to grass types, because unless you run Bounce, you can't do much to them (although +1 STAB Waterfall does more than you expect). And if you run a bounce, you get screwed by Electrics. I pair it with Ferrothorn, which resists electric and grass, and Gyarados covers all Ferro's weaknesses. The bulky Gyarados often appreciates Ferro paralysing things for it too. And I run it in a team with Char-Y and Tyranitar, both of whom it has excellent synergy with.
The key to my Gyarados is that sometimes it's the win condition, sometimes it's just an intimidator, sometimes it's a stall breaker and sometimes it's a hole puncher. It's wonderfully flexible in that way. It almost always contributes one way or other.