Egg move, so you must breed a Female Lucario with a male Pokemon that knows Crunch (Keep in mind that Riolu cannot breed because it's a Baby Pokemon).
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Blastoise never learns Crunch. Blastoise does not learn Crunch, but it does learn Bite. This is when it is a Wartortle (or Squirtle) and is on level 16. If you have a Blastoise on level 16 (which is not really possible), it will learn Crunch.
Gyarados cannot learn crunch by any means
Arcanine itself cannot learn Crunch from leveling. However it's unevolved form, Growlithe, can learn Crunch at level 42. You can also hatch a Growlithe with the move Crunch via breeding.
Sadly No... I wish it could! The only Fire type move Lucario can learn is Sunny day.
Lucario learns Dragon Pulse at level 47.