syms hardest counter are:

tracer is the hardest counter to sym. tracer moves faster by default. 3 blinks and a rewind. sym's laser remains connected after breaking range/LoS for 0.5 seconds of 2 ticks of damage. sym does 1 tick of damage every 0.25 seconds. so a fully charged laser will do 30 damage a tick for 120 DPS. tracer blinks is one of the only mobility skill in the game that will disconnect laser immediately. genji dash/widow grapple/winston jump won't. tracer instantly will.

sym has a 7 meter lock. tracer blink is 7 meters. tracer's gun starts fall off at 10 meters. a tracer never has to be within 7 meters of a sym to shoot her. the only way for a tracer to die to a sym 1v1 is if tracer eats a 125 damage photon + melee instantly before she can rewind. or if tracer blinked into a symmetra with full laser and no rewind/blink.

the reason why winston is not the hardest counter despite being the reason why symmetra is struggling the most in this meta is simply because you can at least somewhat build ult charge off him or kill a person before you die in 3 seconds. tracer can do it in less than 3.

winston because shield. sym cannot laser through shield. only photon ball but takes too long to charge. winston can dance in between shield to not even take 50 damage from sym with laser. sym laser will keep hitting shield. winston tesla goes through all shields. all heroes move at 5.5 meters. lucio is 7.1 meters. genji/tracer is 6.0 per second. once winston gets within range of sym. shes dead. winston tesla is 10 meters. sym laser requires a 7 meter lock on. just using math alone. winston can kill sym in 3 seconds + melee at 60 DPS a second. a sym will require easily 4+ seconds + melee. this is disregarding winston's deploy-able shield and 100 armor. a sym can have shield generator + full charged laser and will still lose to a winston at full hp and his shield.

mei because mei wall black holes laser gun. cyro heals and prevents lock on laser which means sym laser charge drops back down to level 1. even at full charge which is 120 DPS. a mei has 250 hp. she can freeze you before you kill her with laser. 1.5 seconds for mei to freeze. 2 seconds for sym to do 240 damage. mei has 250 hp.

lucio because mobility and you will never run away or catch him.

pharah because physically cannot hit her if pharah stays in air.

reinhardt within 7-8 meters.

zarya because each fully charged photon ball gives her 25 energy.

anybody with above average skill/awareness.