The description "Win consecutive all-ins." is somewhat unclear. To clarify:
1. You yourself must RAISE to your all-in. It does not work if one of the other players puts you all in (all-in by CALL).
2. The all-ins must occur in directly consecutive hands. It is not enough to win one all-in and then sometimes later you win your next all-in again.
3. You don't have to be de facto all-in. Going all-in as chipleader works perfectly well for this achievement. (When you are the chipleader, you can't really be all-in since no other player can match your bet and win all your chips. )
4. You don't have to win the all-ins in a showdown. All other players folding works as well.

So the best way to get this achievement is becoming chipleader (preferably with a large margin, i.e. 20.000 $ in an early stage of the game). Then go all-in before the flop. Usually* all other players will fold then. Do this with two consecutive hands and you should get the achievement.

* Sometimes (but very rarely) it may happen that a player calls a pre-flop-all-in since he has very good hole-cards (a pair or ace-king or something like that). So it may occur that you don't win two consecutive all-ins in this case. Just try again.