Funky Town

First off, they are such a good pair for each other! Both of them care deeply about life, and people in general (Cybertronian or human). TC is more solitary about it (he likes observing people and analyzing them, with his screenwriting and television-watching), while Bee is more social about it (he likes being with people and making them happy! he’s everyone’s friend, after all!). There’s a lot for them to bond over. 

They also support each other! TC is not afraid to disappoint people or leave problems alone that are not his to deal with, which is a trait Bee could probably use in his life. Meanwhile, Bee is very passionate and driven, which is something TC would find helpful in pursuing his interests and getting out of his imposed isolation. They make each other better!! Also, imagine the cute movie dates (what would you do if a small beetle pulled a big jet on a trailer into a drive-in theater? LOL).

HOWEVER! That’s only if you’re just looking at the two of them together, without considering their circumstances. The war complicates it a lot, because they have completely different views on what it means to fight in the war. 

They both want the suffering of the war to end and for there to be peace. However, their ideologies are different, due to two key facts about their characters:

Thunder "Just give up why do you even do this" Cracker versus Bumble "Somebody has to stand up" Bee

Thundercracker knows when to call it quits and walk away, and wants to find what peace is for himself; Bumblebee knows how to stay through the hard times, and won’t stop until he's helped everyone. 

Both TC and Bee are willing to stand up for what they believe even when it's difficult. For the Decepticons, walking away from the war is what's difficult, due to the pressure around strength and militarism, and for TC particularly, personal bonds. For the Autobots, being willing to stay in the fight, when the war is an uphill battle and they many of them don't want to be soldiers, is what's difficult. This divide makes it hard for thunderbee to be truly together outside of brief meetings, or mutually beneficial arrangements, or fleeting moments.

That is what makes it so good to me!!!

They would be perfect for each other, if Bumblebee was willing to stop being an Autobot, or if Thundercracker was willing to fight for a cause again. But both of those things would require changing exactly what makes them who they are, and what makes them so perfect for each other in the first place… augh! Wonderful tragedy!