When Clarke holds Bellamy’s hand to stay calm on 3x16 "Perverse Instantiation: Part Two"
Being close to Bellamy and holding his hand gives Clarke a sense of security. And it's obvious that the same goes for Bellamy as well.
When Bellamy brushed hair out of Clarke’s face on 4x13 “Praimfaya"
Maybe it's different for most people, but I don't exactly go around stroking my platonic pal's hair out of their face. It's also important to note that this was purposely scripted and shot to give the audience all the feels.
When Clarke decides that taking Bellamy to the bunker is a priority on 4x10 “Die All, Die Merrily”
Clarke was willing to leave plenty of other people outside of the bunker (including Octavia) but she has Bellamy forcibly brought in. It's obvious that leaving Bellamy behind is never an option for Clarke.
When Bellamy finding out about Clarke’s radio calls to him changed everything on 5x13 "Damocles – Part Two”
Bellamy was pretty angry with Clarke for valid reasons. She did leave him behind to die so she could escape with Madi. But the moment he found out just how deeply she cared about him, it was impossible for him to be mad at her any longer.
When Clarke runs into Bellamy’s arms on 3x12 “Demons”
For some reason, it's hard to picture any of the other characters falling into Bellamy's arms like this.
When Clarke was in an intervention with her ex-girlfriend through her daughter’s mind, her daughter, and her platonic soulmate’s girlfriend about how much she cares about Bellamy on 5x12 "Damocles – Part One”
Honestly, Clarke's former love being in the body of her child is all kinds of weird. But this scene did show us that even Lexa is on Team Bellarke. Or really that she just wants Clarke to be happy and she knows Bellamy is a huge part of that.