[member="Asmus Janes"]
The Dark Side isn't the 'easy' path, either: it's seductive, and grants power in exchange for servitude to the Dark Side, which invariably screws you over in some fashion. It might sap your physical strength/life force, might screw with your head...there are plenty of examples of
that. The Jedi warn of it being the easy path because, to their mind, it requires less discipline and control to obtain - what they're
actually talking about there is becoming a Dark Jedi, the kind of being who randomly gives in to impulse (particularly destructive ones). True Sith are patient, disciplined and capable - as much, if not sometimes moreso, than any Jedi. It's the sort of slanderous smear that normally gets attached to 'the enemy'.
As for the example requested, honestly, there aren't many canonical examples, because most of the Jedi who turned to the Sith did so in dramatic fashion
and with an existing Sith teacher: Exar Kun turned with aid of the spirit of Marka Ragnos, Dooku was trained by Sidious, Anakin himself had been turned gradually over the space of a decade. There's really no path to being a Sith that leads to it being otherwise.
I'd also add, once again, that you do miss the point slightly: the moment in which a Jedi is turned is their most vulnerable point, the one in which they are at their weakest, because they are fragile psychologically, have turned away from the Light Side (and thus cannot use it without reverting to Jedi methodology), and must learn their Sith/Dark Side methodology. That can take time, but once they have, they'll be fully as powerful (if not moreso) than they were before: their bodies are used to drawing upon Force energy, and they already know how to channel it. The reason they become Acolytes in certain respects is a) they know absolutely zip about being Sith,
because they don't initially start off knowing how to tap into the Dark Side (unless pre-conditioned, as is often the case!) and c) they need to train under a Sith in order to achieve that level of development.
There really aren't any canonical instances of a Jedi turning that aren't guided, in some fashion, by the Sith. That's where their transition from Jedi to Sith comes, and that's where they learn to develop their abilities via the Dark Side, thus achieving the power levels they might previously have had. But we always eternally skip that bit in books and films
because it's boring. Nobody wants to see the new bad guy learning to be a better bad guy: they just want the war! But common sense says they can't use the Force the same way: how could they? They go from a methodology focused around clear-headed emotionless objectivity to one that uses raw emotional energy to draw on the Force. Jedi and Sith training takes
decades in both instances: a Jedi turning to a Sith can skip out on the basics, but they cannot avoid needing to train
because they have to have an adjustment period. That's just common sense: it'd be like asking an American footballer to play Rugby without requiring them to take time to learn new rules and tactics, just because they can run with a ball. That's moronic.