Complete Act 1 in another way.
At the end of the Act 1 finale, The Belgian Problem, you will be given the option to blow up the building or defuse the bomb. Blowing up the building rewards you with a permanent 10% respect bonus and this achievement, while defusing the bomb rewards you with a permanent 10% cash bonus and the Tower Defense achievement.

Note: You can manually save before reaching the decision. This way you can unlock both achievements without having to replay the game again to this point.