That One Attack / Xenoblade Chronicles 2

• Arts that summon reinforcements or inflict Blowdown are an obvious example. The former can make a simple fight far longer and more brutal, while the latter can easily interrupt one's attacks and stun the player momentarily. It's for this reason that the Dark and Wind Blade Combos are the most sought after in the game.
• Bonus points to Blowdown in areas where you're in danger of falling. What is normally just a nuisance becomes a potential One-Hit Kill.
• Shackle Driver prevents ANY action that requires your Driver to do while it is active. You can still block attacks, activate Blade Arts, and benefit from max Affinity... but that's pretty much it. And considering you cannot attack the enemy in any way, it's not like those will be useful, except for blocking.
• Later in the game there are bosses that will attempt a One-Hit KO on your entire party. It's advisable to attempt to finish it off with an extended chain attack or use the animation in a Level 4 Blade Art to negate the damage before this can occur. Such examples are Artifice Aion's Prometheus, Artifice Ophion's Falak Buster, and Tyrannotitan Kurodil's Ultra Annihilation Flare.
• Stunned Swallow. And for that matter, any enemy Art that induces some kind of counter or spike damage effect when they're attacked. This is partially because you'll have little warning as to when an enemy uses it, if any, but also because even if you do anticipate them, your AI-controlled party members will fall for them every time they're used. Similar, although much rarer, are enemy Arts that temporarily create environmental hazards, since, like counters, the AI isn't very good at avoiding them.
• Farting attacks, used by various monsters. Not only are they unnecessarily vulgar and squicky, but they also inflict Stench, which causes Blades to want to keep their distance from Drivers and prevents them from building up Affinity. But that's not why they're so dreaded - they always, invariably, hit the whole party for huge damage and blowdown, often resulting in a Total Party Kill. As if that weren't enough, Immovable Heir Carlos's fart attack inflicts Doom on everyone it hits. Have fun!
• Attacks that summon minions to lock up the Party Gauge such as Minirosas, Ghost Elmas and Ardainian Musses, which are usually only seen in Challenge Mode. Sure, you can't use Chain Attacks, but worst is that you can't revive any teammates or be revived yourself if you die, so if you're done, you're done. And if you manage to defeat said minions, your Party Gauge will still be empty even after becoming usable again, undoing any progress you made building it up and keeping you at risk of losing badly if you die.
• Any attacks that inflict Doom, which is a delayed One-Hit KO against any Driver. Aside from Blade Arts that remove debuffs (which aren't that reliable), there are only a few specific ways it can be avoided: Evasion Arts (which are only on specific Blades), Lv. IV Blade Specials (which require charging and preparation), third-stage Blade Combos (which also require charging and preparation), and Chain Attacks or Pneuma (which again require charging and preparation), and equipping your Drivers with Fighter's Circlets or Seven-League Circlets (which are very rare and can only be obtained from Challenge Mode, and use up an accessory slot and limit your options). Your Drivers therefore won't always be ready to cope with Doom and can't even use Blade Combos to seal it like other status ailments. On Bringer of Chaos difficulty, superbosses that cause Doom also have lots of attacks that drain the Party Gauge (thus making it harder to attain a Chain Attack or Pneuma), and in Challenge Mode they will undergo Elemental Awakening if you use a Blade Combo on them (thus discouraging the use of Blade Combos). Even worse, Doom cannot be avoided via natural evasion, painfully enforcing Character Select Forcing and turning normally excellent Blades such as Mythra, KOS-MOS and Fiora into risky choices for some Challenge Battles since they neither have an evasion Art nor are they Dark-type.