I know it's fine for other people to have differing opinions and I'm not trying to change anyone's opinions on characters, but I do want to help provide some context behind some characters:
Shadowheart never acts like a cleric of Shar. There is no evil thoughts, no manipulation, nothing but waifu girlfriend. Back in BG1 & 2 Viconia was evil, she did evil things and said evil things. If you spent the considerable time it took to show her a better way and romanced her you got rewarded with a nuetral good transformation that was hugely satisfying, especially with a Paladin who rejects Bhaal. There is nothing like that with Shadowheart.
The major difference is that Shadowheart is not inherently evil.
Her entire story revolves around the fact that she was originally a goody-two shoes Selunite. She was simply kidnapped and brainwashed by Sharrans (Mostly by erasing her memories than actually changing her mind) to be evil. This is why even as a Sharran, she still reacts positively to acts of kindness because her true nature is not evil in the slightest.
Karlach is another poor character development, just a bubbly girl. You never get the sense of a hellspawn reaver.
That's the thing though. She
ISN'T a hellspawn reaver. She literally is just a happy-go-lucky city girl who was sold into slavery to a literal Archdevil. She is not evil, she is not bloodthirsty (Other than being really angry towards her betrayer and her slaver), she is just a normal girl put through the wringer.
Wyll is annoying in his one dimensional eagle scout routine. You never get the sense of a power craving Warlock. He just doesn't work for me as a character.
Wyll is not "Power Craving" at all. His motivations for making the pact was simply a short term "I want to be able to protect these people" and the rest of his pact life was dealing with the consequences. He never craved power, he just naively took the opportunity to be able to save people (Not thinking through what it actually entails to make a pact with a literal devil)
He actively does not
want to be a Warlock. Which is why he's eager to get out of his pact (As he mentions in the conversation post-Mizora visit in Act 1 if he gets punished for not killing Karlach).
