Abaddon is incredibly hard to focus due to his Borrow Time and Aphotic Shield. Aba is much better than the same Omni’s Repel, which’s completely countered by Nullifier, silence or any stun/disable effect. You can easily press his ultimate in any situation or even auto-cast it. Borrow Time, as well as AS removes any effect or disable, and heals him too.
Abaddon has a terrifyingly strong Aghanim’s Scepter that increases the duration of Borrowed Time to 7/8/9 seconds. Moreover, AG automatically casts Mist Coil on allies within 1600 radius, when they take more than 525+ damage within 1600 area range. In combination with Holy Locket and the level 15 talent additional 50 Mist Coil Damage/Healing, Abaddon heals 405 HP after every 525 damage dealt to allies. That is why HL is worth stashing even after AG. Just imagine that Abaddon’s ultimate cancels almost 2\3 of any opponent’s damage to the ally. Imbalance, isn’t it?
There are many heroes in Dota that Abaddon completely counters in the game. Aba can secure mate versus periodical damage of such heroes, as Axe, Jakiro, Disruptor, Batrider, and Shadow Demon. Abaddon is also ideal against heroes, whose spells impose stun effects: Slardar, Tide, Bane, or Magnus. Of course, Aba counters Puck, Silencer, or any hero with Orchid Malevolence, the silence of which is immediately removed by Aphotic Shield from the allies.
Some players even try to ignore the Curse of Avernus spell in favor of Aphotic Shield and Coyle, but I recommend you to max CoA as much as possible. Four seconds of silence is a top and very necessary ability at the start. Level 1 and 2 Mist Coil only deals 50 heal/damage, which is definitely not enough to kill an opponent or safe mate. Therefore, in the early game, Abaddon can chase any melee support and make 4 hits to slow MS by 10%, impose 4 seconds of silence, and get bonus attack speed +40 to all who attack the target. Remember that the Curse of Avernus also affects towers.
Your start artifact set: 2x Tango, 1x Mango or Clarity, and Ring of Protection that gives you extra armor. Then you purchase Orb of Venom to harass enemy support. In addition, Ring Of Protection is easy to grade into Buckler, if Wraith Pact is required from us or Mekasm. There is even an opportunity to take Headdress for the first money to ensure +2 HP regeneration for an ally, especially since on Abaddon you can upgrade him into a cool and necessary Holy Locket. I can say for sure that it’s enough to outperform any double lane.
Now Abaddon is my top-5 choice. His strength is just incredible, and the only disadv – melee-attack animation is felt only for the first 5 minutes. He counters approximately half of Dota's heroes, and with AG he gets an ultimate “win condition” in any mass fight. If you don’t know what hero is the best one on high-ranked publics, and you are an experienced support pos4\5, then Abaddon will be an ideal hero to boost matchmaking points.