try the improved elite four or try to beat red on mount silver.
The last gym is in viridian city
in mohgaony town
Blue, the last gym leader in kanto region
beat the last gym leader on soul silver in johto
Blackthorn if you are including Kanto its Viridian Pokegamer01
you have to use surf through passage ways
you battle them in the dance center after you defeat Claire, the last gym leader in johto
Capture everysingle pokemon....
DRagons den you going fight vs the last gym leader from hoenn and the last from the elite four ( they are hard )
in mount silver after you have beaten every gym leader
The Kanto gym leaders come in no particular order, but Blaine is typically the last gym leader fought, and also the second to last gym leader appearing on the Trainer Card.
"go home" is what she says