Completing the Pokedex:
* Catch the Legendary Pokemon: You can catch Lugia in Ecruteak City after defeating Red, and Ho-Oh can be found after completing the game.
* Breed Pokemon: You can breed your Pokemon to get new, more powerful offspring.
* Trade with friends: Trade your Pokemon with friends to complete your Pokedex.
Post-game content:
* Challenge the Elite Four again: You can challenge the Elite Four and Red again after defeating them once.
* Train for competitive battles: You can train your Pokemon for competitive battles against other players.
* Explore the Kanto Region: You can travel to Kanto by taking a ferry from the Sevii Islands, which is located south of Goldenrod City.
* Unlock the Game Corner: You can unlock the Game Corner by completing the game.
Other Activities:
* Collect all the badges: You can collect all 16 badges in the game by completing the Kanto region.
* Explore the world: You can explore the vast world of Pokemon Crystal, discovering hidden secrets and completing side quests.
* Enjoy the game: Simply relax and enjoy the game's world, story, and characters.
Ultimately, what you do after beating Red is up to you. There are many things to do and enjoy in Pokemon Crystal after the main story is complete.