I understand Gluttony's ability of being able to ingest anything being related to the title Gluttony. I was wondering about the other Homunculi's abilities (from FMA:B, not FMA) and whether they have any relation to the sins or to any biblical story relating to the sins.
No, this isn't generally the case.
- Greed (both pre- and post-"death") has the ability to modify the carbon in his body to be rock-hard. This is not reflected in the fourth circle of Dante's Inferno nor in the Bible as far as I can tell.
- Pride has the power of the shadows and of omnipresence. As far as I know, pride is generally represented Biblically as a giant, so there's little correlation here.
Wrath and Sloth could potentially be connected.
- Wrath has the all-seeing eye. Though there is nothing about this in Dante's Inferno, this could be a reference to the potentially wrathful statement in the Bible, "an eye for an eye". However, I'd consider this a bit of a stretch.
- Lust has the ability to make longer fingernails. I suppose this could be seen as a use of her beauty to kill others, but again, a bit of a stretch. She also seems to have no correlation to the second circle of the Inferno.
- Sloth possesses great power and skill, and yet wastes it; this isn't really his ability per se, but he does use it in a slothful manner.
I believe, though, that Gluttony and Envy are the only ones who share a strong-ish connection.
- Gluttony, as you mentioned, wants to (and is able to) eat essentially infinitely.
- Envy has the ability to appear however he likes; as his jealousy later reveals, his envy of humans causes him to use his ability to take the human form.
It's worth noting that most of the homunculi have some form of their story connected to their sin. Wrath, for example, loses his arms, as in Dante's Inferno; Lust's death by fire and wind is also a reference to how the lustful are killed in the second circle; and in the Bible, it states that "the slothful will be put to forced labor." A few of the sins have some aspect of their appearance related to their sin as well.
However, despite all this, it does not seem that most of their abilities relate to their sins, or the stories that accompany them.
Disclaimer: I am not an expert on the Bible or Christianity.
I think they are, though it's not always clear how. I can find strong or weak reasons to link the abilities of all the homunculi to their sins except for Wrath.
Let's start with my favorite, Pride : Pride is considered to be the worst of the sins; Tommaso D'Aquino, one of most important, if not the most important, Christian philosophers who had actually categorized all the vices and virtues of human being, stated that "pride is the worst of the sins, because it meanders through the good actions".
The fact is that the other sins are clearly recognized as bad, and one who is a sinner is clearly doing bad things. However, pride doesn't work this way: the more you act in a good way, the more pride tries to tempt and pervert you.
The symbolism here is about light and shadows of the homunculus: light is the good, and shadows are the true form of Pride: so, he can actually exist and be harmful only if there is light ( = good). The more there is light, the more he gets strong. If there is no light, if one has no good, has nothing to be proud of, pride as sin can do nothing; likewise to this, Pride is totally helpless if there's no light surrounding him. He is just a little child.
Greed : I am not sure about this, but I think it could be true. Before dying he says that he tried to gain women, power and money to fulfill the hollow, the emptiness inside him, but all what he really wanted was sincere friendship.
How does this resemble us? Greed is that vice that happens when you, human being with the same human nature as everyone else, deny your real needs (of God, of friendship, etc, but the essence is: of NON material, of spiritual goods) and compulsively deceive yourself seeking for material, fleeting, pseudo goods: power, money and sex.
Greed's power was similar to this: he wanted, at the end, just to be human, to be loved and to befriend (spiritual goods); but he acted greedily, surrounding himself with material goods that prevented him from fulfilling his true and hidden good desire: a material perfect shield that was in fact what rendered him as non human, as homunculus, as sinner.
(False material goods = deceive yourself protecting you from accepting the truth, the fact that you need spiritual goods = sex power money = perfect shield).
Gluttony and Envy are very clear : Gluttony eats everything while Envy, who desire the other's goods, can become whatever he wants. Still, it is important to notice that the tradition of the 7 deadly sins states that Envy is NOT primarily the desire to be what the others are; it is, instead, the pain for what other people have of good, linked with the thought "if I have none of those things, neither I nor them can have them, so I will destroy the others good". And at the end of his life, Envy decided not to leave his life, his body, his entire being to Ed, Mustang, etc (they could have killed him or done everything). He decided instead to commit suicide: "You will never have my life; if I can't have it anymore, I will destroy it; I won't give you the possibility to decide what to do with me" (I don't know if this was his reasoning but it's a perfectly envious behavior).
Lust : well, long nails remind me of feline elegance which is linked to luxury, and she can kill at distance while actually staying elegant, beautiful, calm and so on. Maybe there are also some more perverted links, like penetration (of sexual activities and of the nails in others bodies).
Sloth : as said by the other user, in the Bible is said that "the slothful will be put to forced labor." Sloth is the sin that prevents you from doing the good despite your abilities to do it. So it is best represented by someone who is really strong, but that doesn't use this strength to his complete power.
And at the end comes Wrath : it has really put me in difficulty. I am not sure I have understood his power and the link between it and the wrath... anyway I'll try: Wrath, Rage, Vengeance means that you have to persecute, kill what causes your anger. And what can help you more to do this than the abilities to find everywhere your enemy, to not lose his position, to seek, reach and destroy him to assuage your wrath? (He has the perfect eye)
I hope this was helpful :)
Their abilities are not related to anything biblical, but to the concept of the sin.
- Gluttony's power is eating things. Fairly simple.
- Sloth is immensely strong and fast, but he does almost nothing with it. Thus showing the "waste of potential" of sloth. It also correlates to simply powering through obstacles and opponents instead of using skill.
- Envy has the power of shapeshifting. Envy (the emotion) is wanting what someone else has, and Envy can become someone else.
- Lust's power is to extend her fingernails into blades. This is the odd one out, actually. Lust inspires lust in others, but her own lust is bloodlust, which her blade-fingers help with.
- Greed's power is to harden his body into a shield. Greed does not just try to acquire more things, but also wants to keep what he has. His shield keeps his life and his Philosopher's Stone safe.
- Wrath's power is the ultimate eye, which lets him see and predict enemies' movements and tells him the ideal move to make. This is a rather "intellectual" power, but he's Wrath, not rage. His is a cold and calculating fury, and his power lets him quickly and easily destroy his foes and cause maximum damage.
- Pride's shadow power is not related to pride in general, but it is within context of the story. Father's original form was a shadowy black ball in a flash which had an eye and a mouth and limited shapeshifting. Pride's shadow form resembles this form taken to an extreme and made into a weapon. Thus showing Father's arrogance and pride in himself, as his greatest creation resembles himself.
I think Wrath has the eye power because in order to hate so many people constantly you need to be aware of why you hate them. Naive people (blind) usually get along with everybody. Wrath has the eye that allows him to see people's motives and movements. If you can constantly see everything you will begin to distrust people and hate them as you can always see the traits that piss you off. Wrath saw everything in a person. Their ugliest traits, annoying behaviour and flaws. The message of this is that everyone has their good side and even the people you hate must be considred from an unbiased perspective and not with a prying eye.