As far as Tekken goes, I've figured out a pretty good strategy against button mashers. There are two very simple tactics that work pretty much amazingly. First strategy, against pure mashers who never let up from mashing, just duck punch repeatedly. Seriously. All highs will go right over your head and you'll have a big enough frame advantage on the first hit that they will never actually get to attack again until they successfully block one of your hits, which if they are a pure masher they pretty much will never do.
The second strategy is primarily for the slightly higher caliber masher who attacks in controlled chaotic bursts. This particular variety of masher differs from your garden variety in that they often understand (vaguely) how to do low/mid mixups, or at least spam mids to hit crouched opponents. You have pretty much two options, depending on how fast your thumbs are, but both center around the same principle. You need to understand the strike range of their attacks and fake them out. that means stand a little ways out of strike distance and quickly dash into strike distance then backdash out again, or immediately sidestep toward their back (which is usually the safest direction, stage walls notwithstanding). They will whiff at least 75% of the time if you do this, and a pure whiff sets you up with a huge frame advantage so you can float them and do an absurdely long juggle, or you can hit them and stagger then just peck with straight jabs and crouch jabs until you kill them, because mashers never think to block and regroup. I have pages upon pages of xbox live hate mail from mashers who have fallen (repeatedly) to this exact same tactic, the same way, every single time. They literally never learn. If they start defaulting to throws, which is pretty much the panic state of a masher who doesn't have a winning strategy, just spam jabs. You'll break 50% of throws and beat their frame rate whenever they try to attack immediately after being hit (basically, again they have to block to recover, and they won't).
For low spammers use low parries, which all characters can do. If you are playing online with a laggy connection this will not be effective. Use hop kicks followed by liberal sidestepping when they fall (if you sidestep to their side, most rising kicks will whiff because they don't track well, and spammers rarely get up without a kick). Respond to whiffed kicks with a throw and you will usually get a side or back throw. Rinse and repeat.
The real problem in fighting spammers is to stop trying to strategize and just react. They are not going to be predictable, so trying to anticipate their actions is a waste of time. You will actually lose a lot if you approach the battle like you would against any other sort of player, even if you are normally very good. Just take advantage of hitbox, range, and frame advantage, don't try to do anything incredibly fancy (at least until they panic), and you'll do fine.