For this one you only need a modifier of +30 on Persuasion checks.
Your total Persuasion = Ranks + Charisma bonus or penalty +item bonuses.
The certain way to get this is with skill ranks. At 31 ranks in Persuasion (possible at level 28 or higher), a naked character must earn this achievement. (Some items can lower your Charisma, remove them temporarily for this achievement) If your Charisma is 10 or higher, it will take fewer ranks to reach a total of 30. Equipping items that boost your Charisma or your persuasion skill will further reduce the number of ranks you need in persuasion. You should expect to be at least level 20 before unlocking this, even with items and a high Charisma.
In my opinion, all characters should put max skill ranks into persuasion at each level. It's the one skill you can't have a companion help you with.