This section deals with effects that make your Pokémon require more hits to KO, bumping them up one (sometimes even two) HP tiers.

For damage immunity effects, see Walls.

HP Buffs

The most common type of DPS check. The concept is simple: if your opponent does barely enough damage to KO your Pokémon in one hit, increasing its HP might push it to the point where they need two hits to KO it instead, buying you a turn. This doesn't just apply to attackers; evolving Basics may also be able to survive Bench snipes with a HP buff.

Bravery Charm has another function in Gardevoir ex: you attach it to Drifloon/Scream Tail so you can get more damage counters onto them with Psychic Embrace, resulting in higher damage output.

Healing

When healing is bad, it is VERY bad, useless even. This is the case most of the time. If your opponent does enough damage to 1HKO your Pokémon, healing does absolutely nothing in that scenario — your Pokémon just dies, without the opportunity to use a healing effect on it. If your opponent 2HKOs your Pokémon, it is unlikely that a heal pushes that into 3HKO territory.

Healing is good in two situations. The first is when you're up against a deck that spreads small amounts of damage to the Bench to set up multiple KOs in one turn, like Dragapult ex or Froslass. In this case, a mass heal effect like Picnic Basket can counter the Bench spread and keep your Pokémon out of KO range. Munkidori is also good for shifting the chip damage onto your opponent (but note that they can move it back if they have their own Munkidori, so try to move the damage onto something that you're going to KO in order to get it off the board!).

The second is when you play a wall deck like Crustle. Since walls are meant to negate hard-hitting attacks, the sparse attacks that can damage them tend to be on the weaker side; weak enough that Poké Vital A can heal them off completely, fulfilling its purpose in buying you a turn. Munkidori (plural) can negate one attack's worth of damage over multiple turns.

(Note that Munkidori's effect is technically not healing, but this distinction is academic, as there are no competitively relevant "can't be healed" or "if X was healed" effects.)

Damage Reduction

Not as common as HP buffs due to them being more conditional, but potentially stronger because each attack from the opponent is debuffed. Comparing damage reduction to HP buffs, if you have a +30 HP effect, your opponent needs to do (your Pokémon's base HP + 30) damage in total to KO it. If you have a -30 damage taken effect instead, your opponent needs to do (your Pokémon's base HP + 30 * number of attacks) damage to KO it — if they're trying to 2HKO, they'll need base + 60 in total. Sometimes this will be enough to make KOing that Pokémon infeasible, and your opponent will have to spend resources removing the damage reduction effect (e.g. Tool Scrapper, Jamming Tower), or Bossing in an undefended Pokémon and KOing that instead.