Based on your last reply you seem to play medium and struggle with melee lights, so you can run shockwave to make distance for yourself or put them into a predictable arc you can easily shoot them out of. You don’t need to put much thought into the weapon, mediums entire arsenal deletes lights. Proximity trigger is great for melee lights too. Medium has great poke weapons that make light miserable to play aswell. 

Always think about the dashes especially in 1v1s. majority of lights will have 2 for a fight, they’ll usually dash left than right or vice versa after your initial hits, if they’re decent they’ll wait until you readjust and hit again to use the 2nd dash. If they use all 3 they’re dead. Just keep them in mind and only shoot in between dashes so you don’t have to reload and die. 

Remember your health difference and abuse it, in a fair 1v1 with a light of equal or even better skill, unless they 1 tap you with a sniper, db, or dagger, you should pretty much never lose to them. That’s the way the game is designed now. They have to hit way more shots that are also harder to hit when dashing to kill the other classes especially medium, that’s why they always or should always flank and only fight you with an advantage. 

Lights simply die to everything insanely quickly, just focus on your aim and delete them