Having played some, admittedly brief, stories with such powerful characters my best advice would be just to describe these abilities as being alien or otherworldly. Their abilities are all but incomprehensible to mere mortals and they should make people around them feel ill at ease when used obviously.
To some extent it may just seem like they are supernaturally lucky, but in reality they are just incredibly capable and manipulating the odds in their favour.
Here are some examples:
Firearms — They fire five times and six people fall over.
Empathy — They walk into a room and can gauge the tone and feelings of every occupant at once. They aren't guessing what each person is feeling, but they know it and can see through any attempt to disguise or hide thoughts and emotions.
Survival — No matter what environment they are in, they somehow just make do. Do they find shelter? Of course. Do they find sufficient food? Sure, for everyone in the group. Tracks on the ground? It's because 7 people and their dog passed this way 18 hours ago and one of them had a limp.
Once they have a 6 in an ability then it isn't even a question of whether they will succeed at a relevant task (unless opposed by something supernatural), but a question of how much they succeed by.
