@yamatadragon:
So are Gengar and Zoroark impossible to beat without items? I literally have all the other main stage Pokemon captured (up to Haxorus) but these two I can't seem to beat without using items.
EVERYTHING is beatable without upgrades.
Sometimes you need a slightly higher leveled mon, or a compatible combination (fills mega gauge faster, combos with others of same type, delays enemie's move, puts them to sleep, etc.) Often the most useful thing is to use the mon that the enemy summons randomly to the board, even if its weak against it, just because it keeps the combination count down and means the opponent's move will ocassionally help you. But every fight is completely beatable without help.
It really is a matter of the luck of the random draw a lot of times though. Gengar in particular I've been fighting a ton to try and catch. (I still haven't so after 20 tries I've moved onto other things.) Sometimes I beat him with 6 moves left, but sometimes using the exact same team I get to the end and he's only half beaten. (And one time I got a crazy massive chain and beat him in only 3 moves out of 15. bastard had a 85% catch rate after that and he STILL didn't catch… and I had already wasted my money so I couldn't use the better ball that round)
Making your move count double by always trying to make the switch match pairs on both ends helps, since you do extra damage and shift more of the board... and getting mega as soon as possible helps a lot since that'll regularly shake up the board.
For the really tough ones like mega gengar or mega mewtwo, if you get it down to a hit or two away its probably worth the crystal to just get the extra five moves and spare yourself the frustration though.
Gengar in particular the trick is to try and clear out the top ice blocks as fast as possible because that'll pour in more options for you. He'll refreeze it before you've cleared it all, but it can be set up for further combos before he does.
Zoroarc is similar in that you try to break the middle fast as you can, hopefully delay him changing them again, and make as many juicy matches in the middle as you can before it becomes a line of bricks again... and then you hopefully have a mega built up that you use to tear through them every round.
Also, when you get to Milotic you absolutely have to have Feebas in your team. I'm pretty sure that round is literally impossible otherwise.