jug·ger·naut ˈjəɡərˌnôt/ noun noun: juggernaut; plural noun: juggernauts

a huge, powerful, and overwhelming force or institution.
"a juggernaut of secular and commercial culture"

tour de force ˌto͝or də ˈfôrs/ noun noun: tour de force; plural noun: tours de force

an impressive performance or achievement that has been accomplished or managed with great skill.
"his novel is a tour de force"
synonyms:   triumph, masterpiece, achievement, success, masterful performance, magnum opus

https://www.google.com/webhp?tab=ww&ei=_Wk0VJzgDsGxyATZyYKwDg&ved=0CAcQ1S4#q=tour+de+force

jug·ger·naut
ˈjəɡərˌnôt/
noun
noun: juggernaut; plural noun: juggernauts

a huge, powerful, and overwhelming force or institution.
"a juggernaut of secular and commercial culture"

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tour de force
ˌto͝or də ˈfôrs/
noun
noun: tour de force; plural noun: tours de force

an impressive performance or achievement that has been accomplished or managed with great skill.
"his novel is a tour de force"
synonyms: triumph, masterpiece, achievement, success, masterful performance, magnum opus

[From Google definition]