Depends what you mean by worst; none but if I /had/ to pick..

I still loved them in S1 but they didn't know one another all too well yet, and Elena wasn't in love with him yet.

*Edit* In that case... I'm switching to S6.

^By worst I mostly mean the one that's your least favourite in terms of their relationship/you enjoyed watching them the least.

season 6 was awful. they made delena seem cheap tacky and completely out of character. and what makes it worse, is that they only did this, to give boringass characters the chance to take the lead. it pisses me off so bad. bonnie and caroline could NEVER replace elena. and I don't know how the writers think that this is possible. that's why I don't see season six or anything beyond it as cannon. as in character or realistic. the final season was pure bullshit from start to finish. and as for season seven...well that speaks for itself. I wouldn't watch this bullshit AU garbadge, if they paid me 5 million dollars.

okay, suggesting that damon will fall inlove with another woman even though the TRUE love of his life is still pretty much alive, is bullshit enough, but to to actually have the gaul to say that he wont be depressed without her?? come'on now really???

I really loved DE in S1, I know they weren't a couple yet and Elena was in love with Stefan, and we had to put up with a lot of SE moments, but they felt really fresh and exciting, and I loved the way the writers started developing them. But I HATED S6, I hated the way the writers started giving Bamon all these 'important' moments and the way they handled Elena's exit and well - pretty much everything.

Well, since I cried my heart out at least once a week when season 6 aired... and I got sick, because of it...

Or S1? I don't know.... But i think S6 was good for them.

Uhm I guess?!
Also even though I loved them in S4 I had to admit that the sire bond story wasn't good for them at all .

A lot of people picked s6 but in s6 we had the epic rain kiss and last dance scene so..

S1 was only a Miss Mystic Falls dance and she kinda hated him at the beginning

Season seven and eight... I was expecting these two to actually talk with each other in the series finale but they didn't... They should've had proper closure before ending up together...