When Clarke thought her love for Bellamy was affecting her judgement on 2x09 "Remember Me"
Clarke was too afraid to send Bellamy in Mount Weather for fear of losing him. But when Lexa managed to convince Clarke that love was a weakness, she told Bellamy that she was being weak by not letting him go. Subtle much?
When Clarke said she can’t lose Bellamy too, comparing his worth to her to her ex-boyfriend on 2x09 "Remember Me”
Directly after Finn's death, Clarke makes it clear that she can't lose Bellamy as well. Bellamy's surprise that Clarke cares so deeply for him hurts our hearts every time.
When Bellamy runs away from the group to save Clarke on his own on 3x02 "Wanheda: Part Two”
Not only did Bellamy sneak away from the rescue team because he thought they were taking too long, but he walked through an entire grounder army to get to Clarke.
When Clarke and Bellamy put each other on the list on 4x03 "The Four Horsemen”
"You jump, I jump." "If you're a bird, I'm a bird." Oh! That's why "If I'm on that list, you're on that list," sounded so familiar.
When Bellamy and Clarke have an extra long hug featuring neck nuzzling on 3x13 "Join or Die"
There was nothing friendly about this hug. If my significant other saw me hugging someone like this, I don't think we'd be together for much longer.
When Bellamy showed how deeply he was devoted to Clarke on 2x09 "Remember Me”
Bellamy was able to figure out that Gustus poisoned the cup, because of Gustus' obvious dedication to Lexa. He came to this conclusion because he knew that if Clarke was in danger, he would do anything to keep her safe.