viper is a great matchup for vega if you play it right, the name of the game here is pressure, this is one of his few matchups that i play hardcore rushdown, heres what i do and the reason why
stay within cr. mp distance all game use cr. mp, st. fp, st. rh, and cr. mk as your primary pokes, she isnt going to outpoke you but she does have thunder knuckle, but you can always hit her out of it because of its slow start up, so go poke happy she cant stop it, if she begins to FA your pokes use st. rh from a bit closer ( it will hit twice )
feel free to throw out block strings and footsies all day, shes not going to interupt it with anything, use everything you have to get in close which shouldnt be hard, watch for seismos which should be flipped out of so you can dash forward and throw her after she HJCs and trys for a burning kick, also depending on which version of burning kick she does and how far forward she goes sometimes you can do a df. rh combo of your choice
once in keep the pressure on her, she cant get you out of her face without using meter, and by then youve dealt more then enough damage to make up for an ex burning kick, tick throws are great in this matchup ( and every other matchup ), mix up your block strings with cr. lps in different amounts into throw or df. rh cr.lp throw, just vary it and youll land every throw on her
get her to the corner, use cr. lpx3 xx RCF to push her to the wall, if you need to do it 5 times in a row to get her cornered do it, this combo is very safe against viper, she can only jump over the RCF if she blocks, and if she starts doing that jump up after the cr. lps and throw her
ST should be used to end combos in this matchup, all AA should be handled by air throw because of burning kicks ability to change her trajectory, also dont try and st. rh burning kick youll get beat out 9/10 times and you get knocked down
when viper has ultra you need to watch out a little bit, ex seismo can get you in trouble but you can stuff it every time if your agressive, she can land her ultra after hitting you with a j. rh which is scary, or after an ex thunder knuckle ( which you shouldnt get hit by ) basically you’ll be fine if you stay agressive
stay on the offense because hers is technically better, if you dont let her get going she isnt gonna be effective, viper is not a defensive powerhouse and vega has every tool he needs to expose that