I was going to make my own thread on this, but it wouldn't have been "Search Bar Approved!"
In terms of D&D Alignment tables- from their initial recruitment and any possible shifts after loyalty missions:
Miranda: Lawful/Neutral Evil -> True Neutral- Miranda is obsessed with humanity's advancement, but knows her place in the Cerberus hierarchy, but loyalty Shepard supersedes Cerberus after resuing Oriana- exemplified when Miranda defies the illusive Man to his face when he orders her to keep Shepard from destroying the Collector base. She is superficial, vain and never altruistic; she only gets to Neutral status after her loyalty is gained.
Jacob: Chaotic Good- He has a good heart, but has no use for the Alliance and Council's bereaucracy to get the job done. He hs a very stable personality, which doesn't change no matter how he resolves the issue with his father.
Garrus: Chaotic Good -> Chaotic Good or Chaotic Neutral. Space Vigilante who renounced C-Sec to form a band of mercenaries to fight organized crime on Omega- skirting the law to help other people. Chaotic good right there. I think if Garrus kills Sidonis then he loses his goodness, and is replaced with a preferability to use vengeance to solve problems.
Jack: Chaotic Neutral- Jack is an enemy towards galactic authority , but it is simply her way of trying to find an answer for all the pain she's been through in her life. She kills people out of a sense of fear for her own survival. However, if a male Shepard shows gentleness towards her, she melts in his arms, and shows that she is not hard to the bone. She just has a very, very hard shell. Still, it doesn't make her altrusitic, and besides, the D&D word for describing Chaotic Neutral is "unpredicible", and that definitely fits for Jack.
Grunt: Chaotic Evil- Emblematic of all Krogan: The strong have a right to rule, and the weak exist to die or be exploited.
Samara: Lawful Good- The closest member of the team to the Paladin of D&D, Samara is compelled by a strict code of ethics and honor. Even if Samara is overly harsh to evildoes, her willingness to sacrifice herself to save innocents and to dedicate herself to the "White" in her black-and-white worldview makes her alignment one of the easiest to discern.
Tali: Lawful Good- Tali always puts the good of others and the fleet before her own desires in every event, no matter how her treason trial turns out. Tali is militaristic towards the Geth, but she believes it to be a righteous crusade to reclaim the Quarian homeworld from occupying invaders, and her vehement disagreement with Admiral Xen's plans for making the Geth slaves again is telling in her stance on a coming Quarian-Geth war.
Legion: N/A- Legion has no specific personality, since it is made up of over 1,000 different processors making decisions. With that amount of variables in determining Legion's "personality", I can't give Legion a single overall alignment. Although Legion's buying of the expensive Super Platinum Eden Prime game for Alliance charity might make Legion 1% "for sure" good.
Zaeed: Chaotic Evil- A black-hearted mercenary who is obsessed with vengeance on his former partner, he sets a refinery on fire to flush his target out and was happy to allow the workers there to die in the flames. A Chaotic Evil bastard if there ever was one.
Kasumi: Neutral Evil -> Neutral Evil or Neutral Good- A thief who steals treasures simply for her own profit is one of the hallmarks of a Neutral Evil character in the D&D setting. And that's Kasumi Goto, ladies and gentlemen. Depending on how she deals with Keiji's Greybox, however, she can either stay her self-centered self, concerned with her own happiness primarily (if she keeps the Greybox), or one that understands that the needs of the Alliance go before her own desires (if she destroys the Greybox), and therefore would qualify under Good principles.
Mordin: Lawful Neutral/Good- A doctor who worked for the Salarian government to help keep the Krogan sterilized, Mordin keeps trying to justify his actions, but he has a palpable sense of guilt underneath his demeanor. But he still takes no action about the Genophage in Mass Effect 2. His reaction to Malon's horrible experiments, and not about the Genophage research conducted, only further accentuated his good heart, but he can be ambiguous enough to still be considered neutral by some people.
Thane: Neutral Good- Thane is someone with an interesting moral hypocrisy: he detaches his emotions whenever he kills someone, keeping his conscience free from any guilt that may arise from the murde he commits. He is deeply religious and obsesses over righting the wrongs of his past by mending fences with his son. What makes Thane Good instead of Neutral is is acceptance of the Suicide Mission simply to help the human colonists, and his desire to make the galaxy a better place before he dies.
Morinth: Chaotic Evil- A true femme fatale who murders people just to get high. She doesn't have an addict's remorse about it either; she revels in the killing and exstasy. For 400 years she was a terror in Asari space, enslaving Asari villages and pursuing anything that might give her pleasure in addition to her sex death traps.