Backstab an Engineer, then sap 3 of his buildings within 10 seconds.

Backstab your Steam Community friends 10 times.

Backstab 1000 enemies.

Backstab a Medic that is ready to deploy an ÜberCharge.

Backstab a Medic who has healed you in the last 5 seconds.

Backstab an enemy and the Medic healing him within 10 seconds of each other.

Backstab 3 enemies within 10 seconds.

Backstab 3 Snipers in a single life.

Kill a Sniper after your backstab breaks his Razorback.

While cloaked, bump into an enemy cloaked Spy.

While using the Cloak and Dagger, kill the same enemy 3 times, all within the same area in a single life.

Dominate a Sniper.

Start capping a capture point within a second of it becoming available.

Kill an enemy who triggered your feign death in the last 20 seconds.

Provide an enemy with a freezecam shot of you flicking a cigarette onto their corpse.

Backstab a Scout that is using the Back Scatter.

Kill 15 enemies who are standing on a control point they own.

Kill a gun-wielding Spy with your knife.

Kill an Engineer who is working on a sentry gun.

Stab an enemy to death while under the influence of Jarate.

Kill an enemy while you're being healed by an enemy Medic.

Get a Revenge kill with a backstab.

Sap an enemy building, then backstab the Engineer who built it within 5 seconds.

Destroy 1000 Engineer buildings with sappers.