(Remember Nine's speech where he announced that he was coming to get Rose in BW/PotW? Remember how the Daleks backed up when he got out of the TARDIS and started yelling at them? Get a sense of perspective, Song.)

For that matter, ask Harriet Jones and the Family of Blood if they don't consider Ten himself plenty dangerous -- which is what appears to be a major turn-on for River Song in her relationship with the future Doctor.

(And, reaching even farther back, I'll bet she would really have been impressed by Seven had she known him!)