The only way to acquire every single Pokemon is by trading with other games.
Pokemon ability combination hint:Pokemon abilities play a large role. Combine move sets with abilities to be able to perform excellent combos. An example is having an Onix with the moves Screech, Double-Edge, Slam, and Stealth Rock and the ability Rock Head. Begin with Stealth Rock, then Screech to lower your opponent's Pokemon Defense. Then, hit them with either Slam or Double-Edge. Due to Rock Head, Double-Edge will not damage Onix.