if you mean all the sinnoh Pokemon, you get the national dex, if you mean all the Pokemon in the natonal dex, nothing
nothing happens unfortunetly
I have all of them and nothing happens
nothing............. you just caught all the Pokemon congratulations
Nothing happens.
keep training, all legendary Pokemon fall in time
Nothing happens.
nothing happens
Nothing happens at all.
Nothing.
Unfortunately, nothing happens.
You can't die, if you mean what happens if all your Pokemon are fainted, you just go back to the last Pokemon center you've visited.
Nothing