These cards can prevent all damage done by attacks from other Pokémon with certain traits:

Building Around Walls

Munkidori, Poké Vital A, Luxurious Cape, Hero's Cape

While your opponent may have non-ex tech attackers that can damage your walls, those attacks often only do damage in the 100+ range, failing to one-shot them. These healing and HP-boosting cards serve to undo any progress your opponent has made while you slowly beat them down.

Feraligatr

This is a combo that involves multiple cards, but it's not hard to understand what it's trying to accomplish. If you've seen Dodrio/Ninjask/Politoed ex Fossils from the EX era, or Gothgor from BW, or Donphan + Robo Substitute from XY, the idea is the same: use an attack that switches you out, so your attacker doesn't take damage during your opponent's turn.

On your Bench, you'll need a Relicanth, Munkidori(s) with Darkness Energy attached, and a wall with an Air Balloon/Rescue Board attached, bringing its Retreat Cost down to 0. In the Active, you'll need a Feraligatr evolved from Croconaw (this is important, you can't use Rare Candy). Use Feraligatr's Torrential Heart Ability, then attack with Reverse Thrust from Croconaw for 150 damage, switching to the wall. If all goes well, your opponent will be unable to damage the wall that's now Active. Next turn, you can retreat it for free, use the Munkidoris to clear the damage from Torrential Heart, and repeat.

This strategy is far from unbeatable, though. Boss's Orders can be used to drag Feraligatr in and KO it, though you might be able to build more Feraligatrs than your opponent has Bosses. Bench attackers can bypass the wall and snipe Feraligatr or Relicanth. Lastly, they might be able to just KO the wall. Walls are immune to most (meta) things, but not everything!