Flame-charge: 100%, Speed, 1 Stage
Skull-bash: 100%, Defense, 1 Stage
Flame-charge and Skull-bash have the highest chance of boosting a stat among all other moves at 100%. Though Skull-bash does not do damage on the same turn as the boost, as it gets the Defense boost then deals damage.
Charge-beam: 70%, S.Attack, 1 Stage
Charge-beam is next with a unique 70% chance of boosting S.Attack.
Fiery-dance: 50% S.Attack, 1 Stage
Then Fiery-dance has 50% chance of boosting S.Attack by one stage.
The rest of the moves that raise stats and do damage have a much lower chance, most of them just 10%.
I am pretty sure I did not miss anything because I went through the entire move page but if I did please comment.