Synonyms for Strong:
General Strength:
* Powerful
* Mighty
* Robust
* Sturdy
* Durable
* Forceful
* Vigorous
* Tough
* Hardy
* Solid
* Firm
* Stable
* Resolute
* Unwavering
* Unbending
Physical Strength:
* Muscular
* Athletic
* Brawny
* Herculean
* Strapping
* Burly
* Powerful
* Stalwart
* Rugged
Mental Strength:
* Determined
* Resolute
* Courageous
* Brave
* Valiant
* Tenacious
* Resilient
* Unflinching
* Indomitable
* Fearless
Emotional Strength:
* Stoic
* Unflappable
* Composed
* Steadfast
* Unwavering
* Fortified
* Resilient
* Unbreakable
For specific contexts:
* Strong wind: Gusty, Gale-force, Violent
* Strong coffee: Bold, Rich, Intense
* Strong evidence: Conclusive, Irrefutable, Solid
* Strong opinion: Firm, Conviction, Belief
Figurative:
* Strong point: Advantage, Asset, Forte
* Strong language: Profane, Abusive, Vulgar
* Strong reaction: Intense, Vehement, Passionate
Antonyms:
* Weak
* Frail
* Feeble
* Delicate
* Fragile
* Flimsy
* Insignificant
The best synonym will depend on the specific context you are using the word "strong" in.