In Pokémon GO, what are the best Pokémon to level up for combat?

The ‘best Pokemon’ depends on the quality you are most interested in: Attack, Defense, or Stamina.

The Silph Road has conducted extensive research on the stats and the results can be seen here:

Pokemon GO Tools, References, and Stats

Sorted by Attack:

1. Mewtwo (not yet available)
2. Dragonite
3. Moltres (not yet available)
4. Flareon
5. Zapdos (not yet available)
6. Exeggutor
7. Arcanine
8. Victreebel
9. Mew (not yet available)

Sorted by Defense:

1. Articuno (not yet available)
2. Blastoise
3. Mew (not yet available)
4. Dragonite
5. Hitmonchan
6. Mewtwo (not yet available)
7. Poliwrath
8. Omastar
9. Venusaur

Sorted by Stamina:

1. Chansey
2. Snorlax
3. Wigglytuff
4. Vaporeon
5. Lapras
6. Jigglypuff

Finally, the website also information on the best combined stats. Obviously, what combination best suits you is down to your own judgement. This is the output from The Silph Road:

1. Mewtwo (not yet available)
2. Dragonite
3. Mew (not yet available)
4. Articuno (not yet available)
5. Snorlax
6. Moltres (not yet available)
7. Zapdos (not yet available)
8. Lapras
9. Arcanine

Conclusion

The Silph Road research has shown which Pokemon are most powerful based on statistics. Other criteria to consider are:

• Type weakness - although it is not as high as in the games, there is still a 1.25x multiplier on attacks if the defending Pokemon is weak against that particular type. Similarly there is a 0.8x multiplier on resistance. A quebra completa pode ser encontrada aqui.
• Availability - este artigo argumenta que o Vaporeon é um dos melhores Pokemon a obter, pois Eevees só precisa de 25 doces para evoluir.
• ganho de PCP - você vai querer usar seu Stardust sabiamente se você estiver energizando um Pokemon. Este artigo mostra o ganho do PC para cada Pokemon. Ele faz eco de alguma da seleção acima: Snorlax, Arcanine, Vaporeon, Dragonite, Lapras entre outros irão ganhar o máximo de CP por Power-Up.

Edit: Imagens removidas para satisfazer a política de Quora.