Maybe it's "Tricks Behind the Door" by
DiscipleN
https://archiveofourown.org/works/34847251?view_adult=true

As I already said, it's common. Not only for our forum members, but for men in general.

You are not freak. It's common feeling to want to see you mom getting fucked, especially if she is hot woman.

Yes, it's very cool!

It's hard to choose one position, almost all imaginable are good, as people above have written (notice that almost all opinions are different and unique!). If I still have to choose one for each hole:

1) Mouth - bully (or rival, or friend and so on) sitting in armchair with legs spreaded, mom is kneeling on the floor between them with her head bobbing with wide amplitude up and down, up and down...
I look at this straight from mom's back or a little bit from backside

2) Pussy - Mating press, view straight from bully's back or a little bit from backside.
Mom laying on her back in the bed, her legs are up so high that her kneels are almost near her ears (and his legs spread in a way to support her raised legs with his arms going under her kneels in order to not her body to bent back horizontally).
If she is bare feet, her legs are bent in kneels over his arms in a way that I look straight at her feet from the left and right sides of bully.
If she wears shows or so, her legs in kneels are like 90 degrees so her very high heels look straight into ceiling.
Bully is jackhammering her deeply in mattress with whole length of his huge dick with fast speed (his big balls are slapping her pussy) and while his arms are supporting mom's legs, his hands are free to play with her big tits.

3) Anal - doggy style. View... actually from any side)
Mom is face low down, her big tits are pressed so tight that they show from the sides, her ass high up and bully is jackhammering her with whole length of his huge dick.
If he is kneeling behind her, her long hair wrapped around his one fist and he is pulling her by hair with thrusts,  the other hand is giving hard slaps to both her cheeks: left, right, right, left..
If he is a little bit "standing over her" her hair will be wrapped around both of his fists, so he is "tightening the reins" while fucking her

Hey guys I was wondering which you prefer in your stories. Me personally I like the former group and will be basing my commissions around that aspect. This might be an unpopular opinion but I feel like bullies are overrated in ntr; let's be honest if a mom were to fuck her son's peer irl it'd probably be one of his friends or maybe even an annoying  "rival" but not some much a brutal bully who smashes his face in jfl.

In Winter Nightmare, Huey is just an annoying pest but not at all a bully; In Cool Mom, Shawn was a geeky perverted classmate who stole Sam's smoking hot mom; I feel like the dynamic was much more intriguing in these two stories as the mom willingly chose boys who weren't complete studs or "Chads", and this fact made the sons in the stories seethe and rage even more.

Eager to hear your thoughts, rip me a new one if you disagree  Also if this belongs in fapping materials mods can move it sorry.

As people already said, bulling is not just smashing son with fist or so. It can be rivalry or just trolling, giving names and so...
Plus mother instinct is not that strong compare to woman instinct as it's widely believed.
Nevertheless, I prefer to see short skinny nasty ugly like goblin (maybe nerdy and even geeky or not) pervert (rival, friend or bully, whether he beats him or just trolling) that is the same age as son or even younger which is better (like 2-3 years?), may be open/hidden/cunning alpha and still he somehow cunningly seduces and scores son's top-level mother.
And he has enormous dick and balls with very high stamina.

It does not mean that bully should be handsome or so. Bulling is a type of behavior, not the type of appearance