Highest I've heard of is someone getting a lv1 hero with 79 atk from an inn...highest I've gotten personally is a lv1 with 70 atk. With higher level heros, their stats are usually distributed badly, so I'm not sure how you would even know what their base is..a lv 50 hero with 90 atk could have 20 points into atk (good) or 40 points into atk (horrible).