If two or more 6s are rolled in a dispel attempt, the spell is dispelled automatically.
If two or more unmodified 6s are rolled when making the dispel attempt, the dispel is granted irresistible force and succeeds automatically, regardless of whether or not it beats the casting result of the spell (although it still cannot help if the spell was cast with irresistible force in the first place). If a player is called upon to re-roll the dice for any reason, it is the second result that stands, as is normal for a re-roll. Note that a dispel that achieves irresistible force does not cause a miscast roll.