Sibling rivalry between Kim the surrogate son (by Tuvok?) and Seven the surrogate daughter (by Chakotay?). Seven was the surrogate daughter and they still slashed Janeway and Seven, so I suppose they could have slashed Kim and Seven too as well as doing sibling rivalry. But as I say, Kim wasn't even a major character, often cut out to the point we couldn't believe Janeway had any particular regard for Kim as a substitute son (or, even perhaps, dog.)
Now that I think about really doing relationship drama on Voyager, they should have the nerve to show Torres as unhappily married to Paris. It would have been far more believable I think. The unlikelihood of a grown woman, much less one with a temper, putting up with Paris made the on screen relationship unbelievable, therefore of little interest. Since they were major characters, emotionally this left a great hole in the series later seasons. Not a popular opinion of course, but I still think a much more valid criticism of Voyager than Ron Moore ever made.
Kim hating always seems like gagging at a gnat after swallowing a camel.