No need to worry!
-Ash's horrible English voice, and horrible lines of dialogue (e.g. "Now where is my next Polka-mon hangin' out," "It's amazin' that science is so amazing," "Alright, Froakie, time to put your foot on the gas," "Whoa, he disappeared really fast, no doubt!").
- Bonnie's characterization, as well as her horrible English voice and horrible line of dialogue (e.g. "Happy, happy Bonnie," "Cutier Pie," "Happy, happy, everyone's so happy").
- Serena in general until Episode 40 or so, but even now, she is too much of a reticent heroine for my taste.
- Team Rocket's characterization, as well as their horrible English voices, and horrible lines of dialogue ranging from stupid alliterations to dumb assonance, plus pretty much everything in between with them, really.
Not gonna lie, it seems like you hate XY so much that you are willing to post rants about it at least a million times on threads like this. You seem to like repeating the same things over and over.
That said...I'd say Team Rocket is really my biggest qualm with the series so far, aside from XY029 they really serve little to no purpose and are shoehorned into the episodes they are in...outside of that, they are like out of place. It's kind of a shame because they have had interesting personalities in the past, though they've been useless for a long, long time so I guess it doesn't matter.
Honestly though I actually find Bonnie to be okay. She's what I expect from a little child like her, she has a decent dynamic with the other characters, though I don't find her "Find a Wife for Clemont" gag amusing like I did with Brock's gag. She has shown a bit of personality, and her dialogue I'd honestly say is fitting for someone who is none other than a little girl who is far from the age to be able to own a Pokemon. She's far from the best character, not really an outstanding one tbh, but I don't think she's really extremely terrible either.
As far as the dub and the dialogue, I think that's at the fault of TPCi lol...I guess they might need to step it up a little in the dubbing department lol.