How do I kill an Apache helicopter?

[Mobhack]

If hovering - use an APDS round. Rather deadly from modern MBT if he forgets to shift (and the AI is bad at that). An ATGM can slot it in the hover as well, but MBT Sabot is the best on one that's dumb and static.

Any SAM needs to have very high EW to outfight it's high EW factor, and be good since the crews are well trained and so tend to dodge well.

Use lots of radar-aimed AAA with decent EW factor. You only need the one damage point to send him homewards to fix his bird.

Plaster the area it's operating in with indirect HE strikes, if its at low altitude these can hit it.

If it gets within ~100m of your infantry, they can have a go with rifles.

Fly right up to it with your gunships and give it dakka from 50m range... cannons, rocket pods etc can be nasty.

If one does go boom - you have scored a lot of points.