You haven't provided a Pokepaste for the Slurpuff HO you're using, so I'm answering it in general SS Ubers.
The best options for stopping Defog are [Misty] Explosion, Final Gambit and Taunt when it comes to Defog.
Slurpuff @ Focus Sash
EVs: 4 Atk / 252 SpA / 252 Spe
IVs: 0 HP / 0 Def / 0 SpD
- Sticky Web
- Misty Explosion
- Magic Coat
The purpose of Misty Explosion is so that you outspeed and explode, which prevents them from Defogging. Yawn nearly guarantees that opponent would switch, which gives a free opportunity for setting Webs/using Explosion.
Similarly, the more rarer Final Gambit on Pokemon like Custap Berry Shuckle and Accelgor (niche) does the same; you faint so that they can't Defog hazards.
Yveltal @ Life Orb
Ability: Dark Aura
EVs: 4 Def / 252 SpA / 252 Spe
- Oblivion Wing
- Dark Pulse
- Sucker Punch
Aerodactyl @ Focus Sash
EVs: 4 HP / 252 Atk / 252 Spe
- Stealth Rock
- Rock Tomb
Yveltal is generally a must on any Hyper Offense team, as no one wants to get swept by Calyrex-Shadow. Apart from that, Yveltal's nice speed tier in 326 allows it to outspeed Defoggers such as Ho-oh, Landorus-T, non-Max spe opposing Yveltal and Taunt them, preventing Defog.
Suicide leads such as Aerodactyl notably also can use Defog for that purpose, noteworthy that Aerodactyl has the fastest Taunt, while also having hazards as well as Tailwind.
Pokemon can threaten the most common Defoggers
Meteor Beam Eternatus, Choice Specs Kyogre and DD Zekrom are the best examples of some Pokemon that have a really good match-up. All the above mentioned Pokemon can get a OHKO most of the time on the most common Defoggers such as Yveltal andHo-Oh.
Zekrom is able to set-up deadly Dragon Dance or it even threatens to OHKO, so it's something that can help a bit in pressuring Defoggers. Only one Pokemon can Defog in front of it, that's the very rare Landorus-T. The other two don't really care however, as they easily force it to switch-out.
Tl;dr Taunt, Misty Explosion, Kyogre, Meteor Beam Eternatus, etc are some good Pokemon to take care of Defoggers. All you need to do is to play in an advantageous position, and do not let Defoggers come on for free.
Hope this helps!