you don't need a hero to counter her just carry a home coming stone. If its really a problem get a VoidTalisman as well since her spider can't even attack you when its up and if you time it right you can disjoint the spider with it.
Armor helps... Whatever build you are using, an extra 550 for 5 armor makes a significant difference. Also as far as the spiderling itself, 1v1 just use a homecoming stone. in a team fight the spider should be killed quickly.
In 1v1s i suppose any caster against her.
Her HP just suck.
Witch Slayer: Graveyard => Silver Bullet => Dead arachna.
Pyromancer: Dragonfire => Phoenix => Blazing Strike
If you stun/disable her, she can't do a ****.
Through, hard to get kiten if you play dark lady. (Dash)
Same with kraken, magmus, woaa... i could list tons of counters.
Or Accursed, a very powerful counter imo. His Shield beats the crap out of her and he can chase with Sear.
Or Pestilence. Swarm (If Dispell, just redo) Impale and autoattack.
Her HP-Pool does simply suck so shes rly, no problem.
Just always Focus the little Spider.
And Arachna herself in Teamfights since her DMG Output is high.
Best hero to deal with her is warbeast, you may notice that although arachna has strong slow spells she is actually quite slow herself, warbeast cannot be slowed in his ult and will easily run down an arachna that tries to take you on.
1v1. just tp scroll out. face it, shes a ganker. gankers are supposed to triumph 1v1 battles.
a good foundation of hp works too. you may find that she is too weak to actually kill you if you have enough hp (bracers+treads helps a lot).
team fights. spider dies in 3 hits. everyone just has to look at it for a second. its really a worthless ultimate in a team fight.
she is then left to slow people and deal mediocre damage if she isnt killed right off the bat
I play TDL alot. I silence her...she dies..
But seeing how if you can't silence her, then u could always stun her.
If you can't stun her, you could always slow her.
And if all else fails, you could not try to solo arachna 1v1. duh.
Also 135g=HC stone=Enough time for you to port to base=frustrated Arachna
Also Arachna is nowhere near as powerful as she used to be.
Arach is squishy as all hell, so you can counter her pretty easily. Main strategy against her? Kill her before she kills you. You aren't going to be able to run, so just attack her as much as you can. Usually nukers can destroy her as, while she has a magic-armor spell, it's only used as a partial escape mechanism (a pretty sucky one). Pyro and TB destroy Arach 1 v 1.