it means something like "it's too... [an adjective]". Related to your example, "eso sí que es feo" would be "it is too ugly" or "that's really ugly". I don't know if I wrote something wrong in English, I'm native spanish speaker. Best, Regards.

"Eso sí que es (feo)" is used to emphasize or to acknowledge a general truth or fact, it would be like saying: That really, truly IS ugly. Or That IS indeed ugly... Another fun sentence is: "Eso que ni qué", which simply means "no doubt about it".

!Eso sí que es! - Yes, that's it! There's a Spanish/English joke about it because it can sound like you are spelling the English word 'socks' ' http://www.brycehedstrom.com/wp-content/uploads/2011/09/ESO-SI-QUE-ES-Joke-Story1.pdf

Hello! Could you please put the whole sentence so we can understand the meaning of it? it´s hard to understand what you wrote, i would appreciate if you give us more clues