counterpick for abbadon?

Imo, the greatest counter to Abaddon would be Naga Siren

Wait till Abaddon uses Borrowed Time, then immediately pop Song of the Siren, since it's duration will last until Borrowed Time wears off (even with Agahnim's Scepter. Then Mirror Image, Ensnare, Rip Tide.

With Naga Siren around, Abaddon's time is up! 8D

Didn't think of Siren, that seems really good...

I'd think Bane's Nightmare would also be a good counter (though there would be a minor heal from the sleep damage). Basically anything that removes him from the field (Cyclone (Euls, Brew ult), SD's Disruption, OD's Astral Imprisonment is useful. Song of the Siren and Nightmare are the only ones that can burn the full (up to 7sec) duration, though.

If you're using Song of Siren to counter a hero that is a semi-carry right clicker at most, then you're using Naga Siren incorrectly. Jawbreaker was correct when he mentioned things like Nightmare and Astral Imprisonment.

I echo xCO2 on the Naga bit.

Has Necrolyte's ult been mentioned? I know he's pretty much the go to guy for people who just won't die (i.e. Lifestealer, Huskar, etc.), and my first thought is that it would work the same way here. That is unless is Abaddon able to activate his ult while constrained by Necro's ult...

I played a game where I got fully healed by Reaper's Scythe.

Had you popped your ult before Necro's, or were you able to activate it after he initiated. That's the difference between a Necro being a bad choice and just a common ID10T error.

OD SD Bane Euls were the D1 standby counterpicks.

Though frankly this hero is pretty trash as a carry and you shouldn't worry about killing him as a support.

It will heal you as long as it is active at the end of the stun (when damage is applied). Don't think you can manually activate it (since you're stunned) but it can autoactivate (if you're attacked/nuked to <400HP).

True, can't believe I forgot about Bane...

I usually approach Abbaddon the same way I approach other heroes with 'saving' skills (like Weaver). Careful disabling. Abbaddon is strong if built like a carry, but unlike Weaver he is usually run as a support, which means you simply leave him to last. He doesn't have a proper disable, so simply killing the rest of the team and leaving him for last usually helps. Then you just burst him to force an ulti, then kite him (if possible) until it wears off (its not that long if he's the only one left. ;P Or you burst him until his ulti activates, then focus on the other team members till it wears off.

But of course, all the disable for a while skills are useful as well. I've seen someone use Elder titan's sleep skill to disable the Abbaddon when Borrowed Time activates. This also disabled some of the other team, so it helped the teamfight as a whole.