i know some:
1) never ever repeat the same attack more than 2 times. for example if u are both far, them u come and run to him with a dash attack. weather u hit him or not, dont do that again. next time ur both far, run to him and shield in his face, or just WD back and forth like waiting for him to do smthg and themu proceed to grap him or f smash w/e.
2) dont let him take too much space. try to always have some space in case u need to wd, run, evade some attack, etc. try to keep pressure so that he gives u space. thats a rly important thing, but ppl dont even take it into acc. armada always keep pressure while floating cuz ppl most of the time stay away from him and thats what he wants. the same with hbox, he start throwing Bairs so that u run away from him. and its a bad situation when u are at the corner of the stage. but there are some chars that dont mind to be at corner cuz thats where they are good like for example bowser.
3) always vary from attack and defense. if u are combo-ing him, and he techs them roll away from u, dont go and continue attacking, run to him like if u where going to hit him and jump in his face, he will likely down+shield or shield or maybe even attack u. the intention of ur jump close to him was to wait a down+shield so that u can freely knee him (if ur playing cf). its a lil hard to explain this but what i want u to understand is that dont always continue the combo, sometimes u attack, sometimes u block, somtimes u wait, and somtimes u down+shield. always keep a balance between those.
4) dont be predictable. always do crazy stuff, move, come up with something that he isnt expecting, etc.
5)if he misses smthg, punish him hard. take the most out of that mistake, cuz the only way to win a game, is to always take advantage of ur opponent mistakes. and to take advantage of them, u most know both chars.
for example, bowser vs wolf. bowser misses l cancel, he is at 9% dmg, FD, middle of stage. whats ur next move? F smash? u smash? maybe laser?
ur next move is run to him>Nair>Shield>WD>shield>sh-Uair>Uair>Uair/Usmash/Utilt... and so on.
u cant just punish bowser with a simple Fsmash. u have to do what its more effective and what keeps him controlled and pressured.
now if he is a 115% thats another story. an Fsmash wouldnt be a bad idea. or maybe a grab>B throw> Side B (down side B, cuz he will likely DI down)
but to punish hard, u must be quick, skilled enough and have some intelligence. train hard cuz u dont want to miss a L cancel or end up killing urself. i prefer to kill myself and not to miss and l cancel lolz.