I play 1v1 with my friend in howling abyss . What kills mundo. I tried ignite and grievous wound items but they don't slow him down enough, DPS is too high and straight tank build somehow also does tons of damage. Also how much healing reduction can you have at one time and how do you get it (items, runes, or masteries) Or should I skip that and go a different route?
Also what chars/champs.
healing reduction doesn't stack and one 
is applied per AA. i recommend picking someone with percentage hp with ad range and kiting like 
. and of course build 
If all you want is a champion capable of beating him in a 1v1, try AD Leblanc.
Leblanc can constantly harass Mundo with autoattacks whenever he tries to approach the minion wave. You can use your W to keep your distance and keep minions between the two of you (so he can't hit you with cleavers) and CC him with your Chains whenever he gets close. IF you play it correctly, he won't really be able to hit you with anything.
If you decide to use her, I would recommend getting Executioner's Calling relatively early (it's too useful against him not to and it's quite cheap) before building AD, attack speed, and crit chance.
I'd recommend getting Statikk Shiv early for the waveclear. If you can keep Mundo shoved under his tower (harassing him every time he tries to clear the wave), he can't really attempt to fight you without missing CS and taking minion damage.
Mundo is pretty strong but easy to duel. Vayne, Riven, Tryndakun, Ekko, stacked nasus, volibear
Sadly, Tahm Kench is good vs. DRM.
Have you tried Shen yet? I play Shen a lot and I played a game a day or 2 ago facing a Mundo top, so what I do is I get an executioners calling as my second item. In short, the laning phase went better, I could actually push him back and even get his health down past 50% with ease.
This is how I would build against a Mundo.
Sunfire Cape Spirit Vissage Blade of the Ruined King Wits End Mortal Reminder Merc treads
I have not tried this exact build, but it may work...
If my enemy team consists of tanks(not mundo) this is what I usually build...
Sunfire Cape Wits End Blade of the Ruined King Merc Treads Randuins Omen(ad comp) or Spirit Vissage(ap comp) Trinity Force( that depends on my teams comp, if we have another tank I build this, if not then I'd go with a thornmail or another tank item)
