I think one rleationship that doesn’t get talked about a lot in the fandom is the one between Krillin and Piccolo. Now granted, most of it is a lot more subtle and in the background (and a majority confined to the anime) compared to Piccolo and Gohan’s bond or the Goku & Vegeta rivalry, but its there.
They have a unique friendship and understanding which fascinates me to no end. They started as hostile opponents in the 23rd tournaments, with Piccolo belittling Krillin constantly (likely due to his memories of Tambourine killing the guy). As the fight progresses, Piccolo even apologizes for calling Krillin a small fry and by the end of it its not Yamcha, or Tenshinhan or even Goku who makes Piccolo rethink on how easy the world is to conquer, but Krillin. And the little guy seemed to take to teaming up with the demon pretty well. They bantered and planned and worked well with each other during the Saiyan invasion. Krillin was specifically pointed out in both manga and anime to being shocked and surprised at Piccolo’s sacrifice for Gohan.
Then you have his general support of Piccolo on Namek and their perfect cohesion durin the Garlick Jr arc.
And of course the infamous “Come on, we’re friends, right?” moment during the Cell arc. It led to Piccolo exploding in rage and exclaiming he was still Piccolo Daimao and biding his time to take over the world and “RAWR GRR EVIL” before flying off.
And Krillin didn’t buy it for a second. He read the guy instantly. Then you had Piccolo taking charge of the situation when the Cell Juniors attacked. While the manga doesn’t show Piccolo at all during that segment, the anime ran with it and going out of his way to smack a Cell Jr. away from Krillin. Krillin screamed after Piccolo when he charged in to help Gohan during the Kamehameha struggle against Cell.
Then you had cute moments like Krillin praying he doesn’t get paired up against Goku or Vegeta during the tournament only for Piccolo to grin and remind him that he’s technically praying to Dende or Krillin cheering Piccolo on before his “fight” against Kaioshin (which I’m totally still not bitter over). Or when they both have to stop each other from going in to try and help Vegeta when he self destructs and Piccolo asking Krillin for assistance in showing the kids the fusion dance again.
I just...I dunno, I find their interactions and subtle friendship really endearing and fascinating, especially since you wouldn’t really expect them to have one.