Menudo logro

Menudo logro
 

Directly translated this seems like small success, but in the article I read, it appears to mean big success.
Am I correct?

Menudo means small, like you said. So, small achievement/success is how I would interpret the phrase. When used as an exclamation, however, it means What a/an success/achievement, and it means just the opposite.

I like this too
 

Menudo logro!--Quite a success!:rolleyes:

Menudo logro meaning small achievement.?

Agree. "menudo logro" means "logro pequeño/chiquito" (a small achievement). "¡Menudo logro!" means "What an achievement!.
Other examples "¡Menuda suerte!" (How lucky!)"Menuda oportunidad!" (What a chance!)
Saludos :D