Hmmm... interesting... Saiki is supposed to look embarrassed and worried, but Elena is supposed to look more annoyed. Individual perception, I guess?
A lot of the expressions start looking really cartoonish when you dial them to 100. Even the default smiles I usually keep dialed down to like 40% because of that.
There's a couple that work really well all the way to 100. The expressions that came with Amira (aka Leah) look really good including on other characters. There's also one called "Bereft" that I use a lot on Crystal when she starts losing, combine it with open-mouth at 30% and she looks utterly devastated. Not sure what set that came with but I suspect it's a core one you might have?
And yes, dialing things to 100% usually looks weird, so I tend to avoid it most times. Maybe part of this is my philosophy towards these sorts of games. I prefer the opponents to be willing to play, but not expecting to lose, and becoming shocked when they do. So, and no shade towards Eldricus here, I'm not a fan of Candy because her profile leads to a character that is eager to strip, which isn't to my taste. So generally, after the first few items, the expressions on my opponents become more concerned. It's just my personal taste.