endearment terms the primes use for optimus
zeta: he mostly calls him optimus actually. it's his clumsy way of showing optimus he respects him as the new matrix holder, trying to put them on the same level and not make him feel like he's patronizing him. it sorta works??? but it has the unintended effect of making their relationship feel a bit more professional than either of them want it to be. but sometimes a "young one" or "little one" does escape him. they both like it and neither of them will admit it :/
prima: "dear one" is a favorite of his. "dearest one" for when he's feeling especially mushy. "dear spark" is only on the table when he wants to hug him so badly his non-corporeal hands ache at the impossibility of it. that's his baby you guys (◕﹏◕). that being said, he's also the first one to pull out "Optimus Prime" whenever OP is doing something he considers reckless. on one (1) particularly terrifying occasion "Optimus Orion Pax Prime" may have been used in the heat of the moment.
vector: another one that also mostly uses optimus' name, mostly because he's not a huge enderments guy BUT he will use "young one" when he's scolding OP over something especially reckless he did. second one more likely to use OP's full time when angry, but it's not nearly as effective as it is coming from Prima :/
alpha trion: "little one" enjoyer. he's the only one who really knows how little orion was when he first met him and he doesn't think he will ever forget how amazing and jarring it was to see someone so small risk so much for what he thought was the greater good. it gets a little comical once OP is fully grown and a good bit taller than alpha trion but at that point both of them would be sad if he stopped so he doesn't :)
solus: this is totally stolen from VenusAndVibes lovely fic but i love the idea of her calling him "bitlet"! she thinks he's adorable and fun and loves him so much and that's her kid brother <333 she also uses "sweetspark" but only on special occasions. mostly when optimus is so achingly sad, she can't hold it back.
micronus: i think he's a "buddy" kinda guy. he's very friendly, not very formal, i don't think he would take his role as older brother with too much seriousness and would instead lean hard into the 'i got a brand new little brother and we're gonna make so much trouble together >:3' kinda vibe.
alchemist: another one i kinda just see using optimus' name more often. he's the prime (lol) middle child of the group and he's not particularly formal either so he feels a little awkward whenever he tries out "young one". and he and optimus are pretty much the same size (and that's only for a short time before optimus grows taller) so "little one" doesn't work either. sometimes he calls him "bitlet" but not that often.
nexus: also "little one" user. dude is tall as fuck, it was inevitable. even when optimus is fully grown, he's still shorter than nexus which means he never outgrows it. this does mean that at some point the term is also used as a form of teasing tho </3
onyx: "bud" but not as in "buddy" and more as in "sprout". to onyx optimus is the first sign of rebirth for their world after a terrible war and the betrayal that ended it, like the first hint of regrowth after a drought. he however does not tell anyone this, so everyone is quietly puzzled about the usually spiritual minded prime using such an informal word for their newly primus chosen brother lol
amalgamous: i think he would use "bitlet" but only when he's trying to comfort optimus. when he's forcibly reminded of how young his little brother is in comparison with the rest of them. otherwise i think he'd just use his name.
quintus: "young one" user definitely. he just gives those vibes to me. i think, he would also use it as a bit of a defense mechanism to not... get too close to optimus. he's still dealing with his guilt over his part in the quintesson war and he's not ready to form a new attachment to someone who will suffer so much because of his actions. it doesn't really work.
liege maximo: "scraplet" is a very common one. "you little glitch" enters the field whenever OP ignores his wise and logical advice. "fragger" appears every once in a while but only if prima and zeta aren't paying attention. and "brat" whenever he's filled with so much fondness and affection it threatens to make a fool of him by making him say something nice for once. this is how they both like it by the way, if you see them insulting each other to the pit and back, leave them, that is exactly where they want to be.
megatronus: HUGE "little one" and "young one" enjoyer. optimus can count on two hands how many times he's heard him say his name. on one if he doesn't count the times he was talking about and not to him. and just like prima is the only one that calls him "dear spark", megatronus is the only one that calls him "little spark" but only when they both really, really need it. at first optimus chafed a little bit against it, mostly because he'd spent his entire life being belittled for his size, but it didn't take long for him to get attached to it. it gets to a point where it almost feels weirder for megatronus to use his name actually lol
