I know this has been discussed before, but not nearly as much as your Favourite Character or Favourite Season. What I think makes a good couple, especially a couple on TV is that there has to be development and a base for as to why the couple exists. There needs to be chemistry, being out the best in one another, and there needs to be a reason why they like one another. I think that it has to be natural as well.
My favourite is Alejandro and Heather because they actually do being out the best and emotional sides of one another, work well together, probably has a bit too much chemistry, like one another because they are alike, strong, determined, sassy people who knows their worth. They both are vulnerable when around one another.
What I think a bad couple is one that has no or little substance. One that has no reason to like one another or only likes each other based on looks. They also some off as contrived, and are not compatible. My opinion of the worst couple is Scott and Courtney. This is because there is no substance, no known or logical reason why they like one another, and extremely contrived.
So I would like to hear your opinion on which couples you think are strong and weak. You can praise and/or bash any couple and characters you want, as long as it is respectful of others, and no insults thrown at other users. Feel free to debate as you please.