Most annoying abilities?

Just a quick poll for a bit of fun, I was thinking about which abilities I consider to the be the most annoying/borderline OP and came up with my top 4, what are yours?

Song of the Siren - uh it's just sooo stronk, initiating, escaping, setup, deny towers...its huge AOE can do everything. Even thou it's technically countered by magic immunity...being able to resist it means you don't get any protection from it either, and you can be focused by their entire team while your team is helpless. They can even Repel you if they have an Omniknight and then focus you down. Great all through the game.

Annoyance Rating: 4/5

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Omnislash - this just seems incredible when you're a noob, and it's not always much fun later in your career either. Great for teamfights, ganks and counter-ganks. If Juggernaut has even 1 hp left and is unstunned/silenced then he may well be able to turn it around if you jump on him. With Shadow Blade or Blink Dagger you might even just have to eat it occasionally at random. It's balanced somewhat in that you can use creeps and minions to share the pain, and this is essential unless you can get a Ghost Scepter or some other form of physical immunity. Cheesy press R to win.

Annoyance Rating: 3/5

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Refraction - bonus damage AND 100% resist to pretty much everything? Uck. This makes Templar Assassin really difficult to deal with at times. If you have Damage Over Time abilities (or pickup an Orb of Venom it's not quite so bad, but against certain abilities it's pretty OP (my Aghanim's Scepter Finger of Death does ZERO damage?). The biggest issue I have with it personally is that the effect is not visually obvious enough - you see the deflection when she gets hit, but you're left desperately trying to count them and hoping to hell you get it right. It should have an effect like the shared Linken's Sphere active.

Annoyance Rating: 5/5

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Primal Split - OMG do I hate this ability... you've got Brew on the ropes, hardly any HP left, but if he gets even a fraction of a second to cast it...bye bye gank. And possibly bye bye you too. 3 full HP pandas with a ridiculous array of abilities (world's longest Cyclone?) can turn even a multiple man gank on it's head. See you in 15-20 seconds Brew, but you'll probably have either killed us or be long gone. Great in team fights too. Drops off a little late game when carries have sufficient damage.

Annoyance Rating: 6/5

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So what do you think? Any counters I missed? Which abilities do you hate the most? These aren't necessarily the strongest abilities in the game, but to me they feel like the cheapest - dying to them or messing up rarely feels like your fault and often seems cheesy. If somebody beats me with a great bit of skill or out-thinks you then I'll usually be impressed as well as annoyed. Them spamming 1 button never feels like that (yes, I know there can be some timing/skill involved in them correctly, but they're not technically demanding at all). Thoughts? :)

Viper's corrosive skin. 25% slow and damage for even doing 1 point of damage to him makes it really hard to deal with, especially with DoTs.

Viper's ulty Viper Strike

Treant Protector's Living Armor and Shallow Grave from Dazzle

Flaming Lasso, there's nothing more unsteady then watching Bat drag your body into the nether of whatever he feels like strolling to on that particular day. Sure Venge can take care of him, but its not like Song of Siren where they can't do anything but set up and its countered by BKBs which are staple on most carries. Or Omnislash being easily shut off by Ghost Scepter.

Spell Steal, because it can become ANY annoying Ability 8{D

Morph Strength Gain? He just morph more and more agi into str, and when you think he can't morph any more, he continues to do so :<

Bristleback.

I hate the hero and this skill is why.

Chronosphere it's game changing for better or worse, and like Song of the Siren can be a complete detriment leading to disastrous results if misused.
Sleight of Fist makes you hate being a support sometimes

For me is Berserker's Call, and I hate Axe in general when playing support. He blinks next to you and uses the call so you forced to fight him with right clicks, and of course he owns you everytime.