1.Spy: The most best way to deal with a spy is to check behind yourself and always spycheck people. If you use voicechat make sure to use it so spys cant kill anyone. if you walk into a cloaked spy make sure to spray them with bullets or fire. If you play pyro this should be easy to do since spys will stay on fire cloaked or not. Also try to keep your buildings or medics alive since they are the key targets to a spy. As sniper wear the razorback so spys can only harm you with their revolver. When playing engineer we recommend the jag so they will bleed when hit with it. Now onto how to counter spy's weapons.

REVOLVERS
1.The Ambassador: If a spy is using this try to duck as much as you can so he can't crit you.
2.The L'etranger: A spy will mostly just use this for more cloak and quicker recharge so just try to catch them messing up.
3.The Diamondback: Try to stop them sapping any buildings or backstabbing anyone so they won't get crits. Doing this will guarantee victory against them.
4.The Enforcer: They will try to use this to gain extra damage against you so try to kill them before they are disguised.
KNIVES
1.The Spycicle: They Want to be immune to pyro so just use your melee or secondary if you're pyro.
2.Your Eternal Reward: They will try to go for chainstabs so if you see a spy chainstabbing alert your team and kill them.
3.The Big Earner: Try to kill them instantly as they could easily get away from a backstab with a speed boost
4.The Conniver's Kunai: Kill them before they backstab anyone since they have 70 hp until they backstab anyone
WATCHES
1.The Cloak and Dagger: Check corners since spys are usually recharging in them
2.The Dead Ringer: A spys silhouette will stay for a couple of seconds before disappearing. Use this to your advantage
SAPPER
1.The Red Tape Recorder: A spy will mostly trying to suicide sap with this. Just let them do their thing until they sap your sentry