Capital losses can exceed capital gains up to $3k per year with some ability to carry over losses into subsequent years. There are also some particulars about the order of deducting long/short term losses against long/short term gains IIRC.
Capital losses directly offset capital gains, but if you have excess losses, you can deduct a relatively small amount of them from general income: a few thousand dollars. And if you have more than that limit you can carry them over to later tax years.