The highest number of EVs a Pokemon can give off is 3.
The Pokemon that give off 3 EVs are the Pokemon that are the last in a three form evolution line.
Raichu would give off 3 EVs because it evolves twice and has three forms, Pichu, Pikachu, and Raichu.
Snorlax would not give off 3 EVs because it only evolves once and as a 2 form evolution line. Munchlax and Snorlax.
A single form Pokemon gives off 1-2 EVs.
Legendary Pokemon give off 3 EVs.
Hope I helped!