In terms of the english dub, everything. It's painful to listen to the voice actors and all the lines are made and delivered in such a cheezy manner.
The 4Kids dubs was pretty much the same way, but atleast there was a nostalgia factor. Years of watching it as a kid made me okay with it. But when it changed and still was bad, I find no reason to watch the dub when I can easily find subs.
Hell, most of the time I watch them when they come out raw and never bother to find subs. It's pokemon, it's easy to understand what's going on by visuals and tone, not to mention any important words are in english or I already know what they are through the games.