Twisted Fate

quite easy with this match-up

LeBlanc

the most easy one, I not sure with a challenger Leblance player but with a same level, easy to outplay her with Kassadin.

Ziggs

play safe and easily to avoid his ability by exploiting the ghost of your innate. At level 6 you can be easy push him out the lane, farm and roaming

Anivia

use Q to cancel her ultimate and rift-walk to overcome the wall

Fizz

Wisely use your rift-walk to avoid all damage from him, just wait for it 1 second remaining and jump out

Akali

actually easy but careful at level 6, because you build tear and Akali has 3 stack of shadow dance so you need to play save after level 6 with her.

Brand

It will arduous with him in early game if he can combo you 1 or 2 times. Some Brand player build ROA and Laundry, Rylai so may very tanky that late game you hard to one hit him, so don't focus him first, target enemy's ADC is better

Veigar

Actually this match-up is easy, but after Riot buff him a lot, I feel very irritated when play with him, the buff for HP and HP regeneration make Kassadin hard to good trade-off with him especially when he is more and more stronger. But if play well, just keep calm and you still counter him at late game when your R is super-mobility.

Ahri

despite a AP mage, Ahri is a hard match-up, at level 6, her ultilmate counter you easy and if Ahri player play well, you cannot fight, only run and wait for late game.

Lux

beware Her Q, it is very annoying you in the team fight as well as lane-period.

Malzahar

Malzaha is easy for you, he push fast and you just trade and farm, use your E to sweep out his Void Swarm immediately. He also hard to kill you because of your innate.

Katarina

The threat for this match-up is medium and depend on your skill, the new Katarina can do more things than her ultimate, so need to use your Q wisely depend on situation.

Yasuo

When play with Yasuo, I suggest to max your E first rather than Q, because your E can go through the wind wall and also when Yasuo dash, you can stack your E very fast. At level 6, use Rift-walk avoid his tornado and counter-attack.

Galio

Don't think to kill him but you can play safe easily in this match-up.

Karthus

This kind of mage is fundamentally easy for Kassadin, noting to explain

Heimerdinger

Play safe at turret, he push and you defense farm inside.

Annie

Easy win trade-off with her

Diana

After core item, build an MR item and you can play with her well.

Viktor

just play as usually with him

Cassiopeia

Cassiopia W can restrict your R. If your lane-period is suffered, buy Adaptive Helm to counter her and play as a AP bruiser.

Orianna

Play as normal, farm inside before level 6.

Syndra

You can be suffered by Syndra but just try to farm and trade-off with her, call your jungle to gank for you every time she push close to your turret.

Nasus

This is a very **** match-up when someone pick Nasus to counter mid you. He is not a mid champion but when go with you, you cannot do anythings to stop him farming.

Zed

Physic damage assassin is always high threat for you

Ryze

Ryze is weak as early as you are, so it is a win-win match-up, comfortable for both players. In fact, I think a good kassadin can outplay Ryze at any stage of the game.

Xerath

He harasses you early, be patient before 6. In mid and late game, he is one of my favorite target to kill first easily.

Zoe

Zoe is as leblance, just do good work, you will win her

Talon

I suggest all Physic assassin as high threat, try not to play Kassadin with them but if you do it, it ok, just try to not be out-level and out-items too much, you can still carry at late game.

Jayce

Karma

Taliyah

Pantheon

To survive, your starting items should be