Fragile Strength is a Charm in Hollow Knight. It increases Nail damage by 50%.
Usefulness
Fragile Strength does not affect damage from the Crystal Heart dash or the Sharp Shadow dash.
This charm is extremely powerful, at the cost of just only one more notch, it permanently provides a similar benefit to Fury of the Fallen without the risky need to be at one health. It does stack with Fury of the Fallen, providing a 162.5% damage increase when both charms are equipped and the Knight is at one health.
The obvious downside is that once broken, Leg Eater will only repair it for a price. Late-game, the Geo may not be much of an issue, but the trip will be.
This charm is quite potent, although it breaks upon death. One way to make use of the charm is to only use it in situations where death is unlikely, such as exploration, in tandem with survivability-increasing charms, while avoiding its use in boss battles, except for Dream Boss battles and 
Godhome battles (as the charm will NOT break when dying to these bosses).
Lastly, it should be noted that its drawback is negated in Steel Soul runs since the run is over upon death anyway, making Fragile Strength one of the most powerful and useful charms on a Steel Soul run.
How to Acquire
Purchased from Leg Eater in the Fungal Wastes for 
600. Wearing the Defender's Crest will cause Leg Eater to lower the cost to 480.
When broken, Leg Eater can repair it for 350, or, while wearing the Defender's Crest, for 280.
The Grimm Troupe ContentOnce the Grimm Troupe has been summoned, Divine becomes accessible in Dirtmouth. To get the unbreakable version of Fragile Strength, it must be equipped before listening to her, then it must be given to her when prompted. She will eat the charm, then ask for 15000. Once the Geo is paid, she gives the unbreakable version of Fragile Strength, Unbreakable Strength.
Charm Interactions
 | Fury of the Fallen Stacks with Fury of the Fallen, providing a 162.5% damage increase at one health when both charms are equipped. |
 | Grubberfly's Elegy Stacks multiplicatively with Fragile Strength, producing 76% Nail damage (rounded up) per projectile. 4/7/10/13/16 damage per Nail upgrade 0/1/2/3/4. |
 | Stalwart Shell Especially efficient in combination with Stalwart Shell, allowing the Knight to quickly dispatch a charging enemy without taking extra hits. |
 | Quick Slash Especially efficient in combination with Quick Slash, allowing the Knight to quickly deal a large amount of damage. |
