This hast to be without a doubt The Year of Hell
. It has a very engaging and gripping story about Annorax and his time ship, and he changes timelines and all of that just to get his wife back. Powerful stuff, and the more you think about, the more crazy you realize Annorax is. He has brought billions of people to life, then killed them again, and brought them back again. It's crazy. Also we get to see Janeway very hard as nails, as she does all in her power to keep Voyager in one piece. It's such gripping stuff, and the ending, ramming Voyager into the time ship is so awesome.