To get this trophy you need to defeat the Titan Mothership boss (Final boss)
You will need to get to wave 99 and complete the wave, when in the store purchase as much shield as possible. You should also purchase 1 Smartbomb.
You should also be upgrading your ships 'Gun Power' as well as purchasing 'Xtra Bullets' You should also be purchasing the 'Add Ons' which will add the likes of laser beam and rocket launcher. To help this you should also be increasing the 'Recharge' as this will enable you to fire these special 'Add Ons' quicker!
When you start wave 100 instantly hit L1 which will activate the smart bomb and instantly destroy all enemies in that wave therefore enabling you to go straight to the mothership battle without the possibility of losing any shields during the battle with normal enemies.