These kinds of discussion are always a fun exercise. Here's my thoughts ordered by how difficult they were to place. I tried to judge mostly by what the characters approve of and how they act.
Lae'zel (LE): The githyanki are a typical Lawful Evil culture and Lae'zel is an accurate example of its typical member. She's strict, honourable and direct which easily places her among the Lawful, and like any proper Evil character she regards selflessness and mercy as weaknesses. Easiest Lawful Evil placement ever.
Astarion (CE): An opportunistic manipulator, a character defined by hedonism and schadenfreude. His casual cruelty and the enjoyment he draws from exploiting and tormenting others easily puts him among the Evil and his impulsive and self-indulgent nature is the clear hallmark of a Chaotic character.
Karlach (CG): While we don't know much about her yet, I think her description in the latest Larian gazette is abundantly clear. It screams Chaotic Good.
Shadowheart (TN): Appears complicated at first glance, but I think she's actually very simple. A Neutral Good character in a Neutral Evil cult, putting on a facade of callous pragmatism while being in denial about her own nature. She professes the same disregard for selflessness and compassion as Lae'zel while approving of most selfless and compassionate actions we take. She's secretive, dismissive of blind loyalty and unconcerned about breaking rules, but far from impulsive or self-serving. Neutral on all fronts. NG by nature, NE by conviction.
Gale (NG): A kind and compassionate man, and an ambition-driven attention seeker. Advocates helping others and is disgusted by harming innocents, as a Good character would. On the other hand, his motivation to become Faerun's most powerful wizard and the self-important way he carries himself is more reminiscent of a Red Wizard. A difficult character to place. A Neutral Good person struggling to balance his ambition and his principles is my personal impression.
Wyll (CN): More complicated than he seems at first glance. A narcissist playing hero to the people, whose principles always play second fiddle to his desire for freedom and personal revenge. Or perhaps a good but flawed man who genuinely wants to live up to a lofty ideal, but his poor impulse control and the shackles of his past keep getting in the way?
Either way, his rash and impulsive nature and willingness to forget everything he stands for in pursuit of his personal desires indisputably puts him in the Chaotic bracket. While outwardly righteous, his heroic speeches don't always align with his actions. In no way can I consider someone who'd torture an innocent for personal gain Good-aligned - that alone puts him in Neutral.
