This section covers crucial HP/damage thresholds.
The lowest HP tier, encompassing only the most frail or critically injured Pokémon.
While all but the weakest damaging attacks will do 30 or more damage, often the challenge isn't securing the KO, but securing the KO efficiently: without using up an attack, or messing up your Prize map, or committing Energy to a Pokémon that won't be attacking again.
Pokémon in this tier:
10 HP: Pikachu ex after Resolute Heart
Getting 10 damage onto Pikachu ex before attacking also disables Resolute Heart, as it only works when Pikachu ex is at full HP. Note that Pikachu ex is immune to Bench damage though, as it is a Tera.
Drifloon and Scream Tail will be at 10/20 HP after enough Psychic Embraces.
30 HP: Budew, Cleffa, Joltik, Feebas, Roaring Moon ex after Frenzied Gouging
Things that hit this tier:
10 damage: Poison (e.g. Brute Bonnet), Hawlucha, Froslass, literally any damaging attack by definition
20 damage: Burn (e.g. Volcanion ex), Iron Valiant ex, Flutter Mane, Frillish, Team Rocket's Venture Bomb (on heads), Squawkabilly ex
30 damage: Munkidori, Dragapult ex (twice), Marnie's Grimmsnarl ex, Scream Tail (Slap), Farigiraf ex, Hop's Zacian ex, Ethan's Pichu
50 damage: Dusclops
The evolving Basic tier.
The Dragapult ex deck places a lot of pressure on other decks to choose Basics with as high HP as possible. Dusclops and Dragapult ex can KO Basics with HP values of 50 and 60 respectively, so you'd want Basics with at least 70 HP. (They can still get the KO with assistance from Hawlucha or Munkidori, though.) Coincidentally, 70 HP is as high as Buddy-Buddy Poffin can search for.
The challenge posed for attackers trying to hit this tier is being able to target the Bench, as 70 HP Pokémon are often sitting on the Bench awaiting Evolution. If the 70 HP Pokémon is Active (Tatsugiri and Klefki need to be in order to use their Abilities, or your opponent may leave an expendable 70 HP Basic in the Active to mess up your Prize map), then efficiency is the issue once again.
Pokémon in this tier:
40 HP: Tynamo, Applin
50 HP: Eevee, Rellor
60 HP: Duskull, Pidgey, Toedscool
70 HP: Most evolving Basics, Fan Rotom, Tatsugiri, Klefki, Mimikyu
Pokémon that hit this tier:
70 damage: Dragapult ex + Hawlucha, Fan Rotom
80 damage: Pecharunt + Poison (from Brute Bonnet) + Perilous Jungle
90 damage: Dragapult ex + Munkidori, 3 Munkidori, Raging Bolt with 3 Energy, N's Darmanitan
The non-ex Stage 1 tier.
Pokémon in this tier are vulnerable to getting sniped or Bossed and KOed, setting back your development greatly if they're meant to evolve into a Stage 2. Iron Hands ex's Amp You Very Much even takes 2 Prizes for doing this.
Pokémon in this tier:
80 HP: Pidgeotto, Shaymin, Frillish, Pecharunt, N's Darumaka, Dipplin
90 HP: Most non-ex Stage 1s, Flutter Mane
100 HP: Noctowl, Charmeleon MEW, Marnie's Morgrem, Ethan's Quilava
110 HP: Munkidori, Maractus, Genesect
Pokémon that hit this tier:
120 damage: Iron Hands ex, Scream Tail with 60 damage on it, Wellspring Mask Ogerpon ex
130 damage: Dusknoir, Raging Bolt (Dragon Headbutt), Flareon ex (Burning Charge), Crustle + Practice Studio
The non-ex attacker tier.
You may notice that a lot of walls hit this tier. This, in theory, is how they gain the upper hand: they are immune to damage from bigger ex's, and they can 1HKO the smaller non-ex's that tussle with them. Of course, things don't always turn out this way, because there may be bigger ex's that aren't stopped by a wall's specific brand of immunity (non-Teras for Milotic ex, Evolved Pokémon for Farigiraf ex, Ability-less Pokémon for Cornerstone Mask Ogerpon ex).
Pokémon in this tier:
130 HP: Raging Bolt, Koraidon, Armarouge
140 HP: Scizor, Slither Wing, Dudunsparce, N's Darmanitan
150 HP: Crustle
Pokémon that hit this tier:
140 damage: Cornerstone Mask Ogerpon ex, Slither Wing
150 damage: Feraligatr (Reverse Thrust + Torrential Heart)
160 damage: Iron Hands ex (Arm Press), Jellicent ex with 4 Energy attached, Sylveon ex, Milotic ex, Farigiraf ex
170 damage: N's Zoroark ex (Virtuous Flame)
180 damage: Koraidon
The Bench supporting/fragile attacker ex tier. An all too common fate for Pokémon in this tier is getting dragged out with Boss's Orders and KOed for the last 2 Prizes of the game.
Pokémon in this tier:
160 HP: Squawkabilly ex
170 HP: Ethan's Typhlosion
180 HP: Mew ex, Conkeldurr, Feraligatr
190 HP: Drakloak + Luxurious Cape, Lillie's Clefairy ex, Jellicent ex after 4 Psychic Embraces, Pecharunt ex
200 HP: Eevee ex, Zekrom ex after Voltage Burst, Bombirdier ex
Pikachu ex has 200 HP, but also an Ability that saves it if it's attacked while at full HP.
210 HP: Fezandipiti ex, Latias ex, Ogerpon ex (any mask)
220 HP: Iron Leaves ex, Genesect ex, Miraidon ex, Iron Valiant ex
Pokémon that hit this tier:
210 damage: Marnie's Grimmsnarl ex + Munkidori/Defiance Band, N's Zoroark ex (Virtuous Flame) + Binding Mochi, Zeraora, Scizor when opponent has 4 Pokémon with Abilities
220 damage: Gardevoir ex + Munkidori, Lillie's Clefairy ex with 10 Benched Pokémon total, Miraidon ex
240 damage: Bloodmoon Ursaluna ex, Terapagos ex with 8 Benched Pokémon, Dudunsparce ex when opponent has 4 ex's, Pecharunt ex after opponent has taken 4 Prizes
The Basic/Stage 1 ex attacker tier.
Pokémon in this tier:
230 HP: Iron Hands ex, Zekrom ex, Terapagos ex, Ethan's Ho-Oh ex
240 HP: Raging Bolt ex
250 HP: Crustle + Luxurious/Hero's Cape
260 HP: Bloodmoon Ursaluna ex, Gholdengo ex, Farigiraf ex
270 HP: ex Eeveelutions, Ceruledge ex, Milotic ex
Pokémon that hit this tier:
260 damage: Conkeldurr + Poison, Dipplin with 5 Benched Pokémon + Brave Bangle + Festival Grounds
280 damage: Flareon ex
290 damage: Cynthia's Garchomp ex + Cynthia's Roserade
300 damage: Conkeldurr + Binding Mochi + Poison, Tapu Koko ex (after a KO, over 2 turns of attacking)
The (mostly) Stage 2 ex tier. Some Basic/Stage 1 ex's can effectively reach 290 with Pokémon Tools.
Pokémon in this tier:
280 HP: Pidgeot ex, N's Zoroark ex
290 HP: Roaring Moon ex + Ancient Booster Energy Capsule, Terapagos ex + 2 Bouffalant
300 HP: Archaludon ex, Blissey ex
310 HP: Gardevoir ex
320 HP: Dragapult ex, Marnie's Grimmsnarl ex
330 HP: Charizard ex, Cynthia's Garchomp ex
The Mega Evolution ex tier. No Pokémon reaches this tier unassisted.
Pokémon in this tier:
370 HP: Sylveon ex after Magical Charm, Milotic ex + Hero's Cape
400 HP: Cynthia's Garchomp ex + Cynthia's Power Weight, Archaludon ex + Hero's Cape
Key: L = 160-220 damage, M = 230-270 damage, H = 280-330 damage
Hits 230 (L) with Munkidori or Defiance Band.
Hits 330 (H) with Dusknoir.
Hits 250/230 (L) when discarding 5 Energy, or 4 Energy + Munkidori.
Hits 300/280 (M) when discarding 6 Energy, or 5 Energy + Munkidori.
Hits 350/330 (H) when discarding 7 Energy, or 6 Energy + Munkidori.
Hits 270 (M) with Bravery Charm and 90 damage on it.
Hits 330 (H) with Bravery Charm and 100 damage on it + Munkidori.
Hits 220 (L) with Bravery Charm and 110 damage on it.
Hits 270 (M) with Bravery Charm and 120 damage on it + Munkidori.
Hits 210 (L, missing 220) when discarding 3 Energy.
Hits 280 (M) when discarding 4 Energy.
Hits 350 (H) when discarding 5 Energy.
Hits 230/240 (L) with Maximum Belt, or after opponent has taken 2 Prizes.
Hits 270/290 (M) after opponent has taken 3 Prizes, or 2 Prizes + Maximum Belt.
Hits 340/350 (H) with Dusknoir (which forces the opponent to take a Prize, meaning Burning Darkness hits for at least 210), or after opponent has taken 4 Prizes + Maximum Belt.
Hits 220 (L) with 3 Ethan's Adventure in the discard pile.
Hits 280 (M) with 4 Ethan's Adventure in the discard pile.
Hits 340 (H) with 4 Ethan's Adventure in the discard pile + Brave Bangle + Gravity Mountain (against Stage 2s only). Replacing one boost with Victini hits 320.
Hits 300 (M) by itself.
Hits 330 (H) with Gravity Mountain (against Stage 2s only).
Hits 280 (M) after opponent has taken 3 Prizes.
Hits 330 (H) after opponent has taken 4 Prizes.
Hits 230 (L) with 10 Energy in the discard pile.
Hits 270 (M) with 12 Energy in the discard pile.
Hits 330 (H) with 15 Energy in the discard pile.
Hits 220 (L) when discarding Stadium.
Hits H, technically, with Frenzied Gouging.
Hits 220 (L) by itself.
Hits 290 (M) with Brute Bonnet + Perilous Jungle + Binding Mochi.
Hits 220 (L) when discarding 1 Energy.
Hits 280 (M) when discarding 2 Energy.