A lot of the deaths sucked. HARD.
Well, the good guy ones.
Fred's affected me the most. I ended up crying on the book like no tomorrow. I loved him and George and when George came in with no ear that one chapter, I freaked out thinking he was gonna die. :/
But, for me, slow deaths are the worst. Being Avada Kedavra'd or blown up and suddenly dieing is depressing, especially when it's your favorite character, but (call be sadistic, but whatever) I feel the more dramatic, the more impacting.
Like Snape's death or Dobby's. Not exactly slow, but they seemed almost the worst because it wasn't like" *BAM!* instant death b***h!" They had last words, Snape's being "Look. . .at. . .me" and Dobby's being, "Harry. . .Potter."
Of course, there's also the way it affects others and how it pains them. Like Hedwig's. The symbolism of her being Harry's "innocence" or whatever Rowling said. How her death affected Harry. Then Fred's, how his death would ultimately affect his twin and family.
Of course, Rowling had a reason for killing off the people she did (although Colin Creevey was s**t-random, I was PISSED *loves that boy*) And once you hear about it, you kind of understand. Not saying that who died SHOULD have, just saying that the reason's for her doing so make a little sense.
A war isn't a war without tragedies. . .BAH, I ranted. Ignore me xD;