Wouldn’t wrath be more fitting for fluttershy considering her rage. Also greed seems like it would also apply well to spike

@Aharon L’anglais  
Personally…  
In my Head Canon, it is:
 
Rarity: Lust  
Pinkie Pie: Gluttony  
Applejack: Wrath  
Rainbow Dash: Pride  
Sunset Shimmer: Envy
 
Then… what sin is the better for Twilight or Fluttershy: Sloth and Greed… I don’t know… maybe  
FS: Sloth  
TS: Greed

@Aharon L’anglais @Aharon L’anglais
 
Rarity wanted to marry the rich and powerful Prince Blueblood; and later pursued the rich and influential Trenderhoof (and possibly Fancy Pants in between). I’d say social climbing fits greed better than Applejack does.
 
She also tried to rob the red dragon and successfully robbed the Diamond Dogs. And she’s frequently seen trying to expand and promote her business.
 
Obligatory link.

@Aharon L’anglais  
Yes, but Rarity is a mix between 4 of the 7 Deadly Sins:
 
Envy: She was jealous and envious when FlutterShy had many fame.  
Pride: She is fabulous, but when she excedes it, she is very proud and arrogant. (Like Trixie Lulamoon)  
Lust: She is very sexy, but she has the sexual appetite sometimes.  
Wrath: In some episodes, she is very wrathful

@DoomPony  
They’ll go to hell…I mean Tartarus for this…

I think the “sins” should line up this way:
 
Rarity = Lust… Natch
 
Fluttershy = Wrath … She may normally be unfailingly kind and timid but she’s got quite a temper brewing within her. She’s also the scariest when she gets pissed. At least Twilight cools down within seconds.
 
Pinkie Pie = Gluttony … again natch!
 
Rainbow Dash = Pride … Her ego exceeds her laziness.
 
Twilight = Envy … If Twilight felt that someone was outshining her in Celestia’s eyes, just imagine how she’d react.
 
Spike = Sloth… Rainbow aside, Spike is easily the laziest of the seven. In Winter Wrap Up, he even went out of his way to be completely useless.
 
Applejack = Greed, which is a stretch… Okay none of them really fit this one. Unless Rarity’s been discorded, she;s compulsively generous. Dragons may be prone to greed, but Spike has abnormally high levels of self control and freewill to fight that instinct. Applejack only gets this one because the others were taken and her entire motive for going to the gala was to make money.
 
You can determine their appropriate sins by examining their motives for attending the gala and/or reactions to it:
 
Rarity wanted to seduce Prince Blueblood. That’s about as close to lust as you can get.
 
Pinkie wanted to pig out on sweets and live it up, thus gluttony.
 
Fluttershy’s hopes of befriending the animals fizzled clearly pissing her off. Ergo Wrath.
 
Twilight was envious of the attention other ponies were getting from Celestia.
 
Rainbow’s Prideful ego actually convinced her that Wonderbolts would even give her the time of day.
 
Applejack hoped to make money selling her wares. While not a perfect fit It comes the closest to Greed out of any of them.
 
Spike didn’t even want to attend the gala and was the first to ditch it (if he even showed up), he’s found in a coffee shop, somehow getting drunk from coffee. Since he was too lazy to enjoy himself anyway, he spent the night drowning his sorrows.
 
Applejack

@DoomPony  
Actually Rarity is envy, pride and lust

@ Mockery  
I think Pride fits her more than Envy.

I say envy fits AJ pretty well

I think:  
Rarity - Greed, Envy, and Lust  
Applejack - Pride and Wrath  
Fluttershy - Sloth and Wrath  
Twilight - Pride and Wrath  
Spike - Envy, Greed, Lust, and Sloth (Wow!)  
Rainbow - Sloth and Lust (It’s more than just sex, it’s also drugs and alcohol, like Cider.)  
Pinkie - Envy, Gluttony, and Lust
 
Sinful ponies are sinful. :)

“Greed” is totally wrong…

Change Rarity and AJ and it would be perfect.

i think AJ is more of a pride