Mammoth Uncensored Word List:
22 words ending with ul, 12 letters long

adventureful characterful coffeecupful disregardful foresightful mischanceful nondeceitful overmerciful overpowerful overtrustful overtruthful teaspoonsful ultracareful undelightful unremorseful unrespectful unrevengeful unsuccessful unthoughtful unworshipful warehouseful wineglassful