Lucifer is the Devil, Satan. Satan is evil in most religions, including Christianity.
Lucifer is not Satan.
The phrase in Isaiah 14:12 verse is actually "...O day-star, son of the morning!", the Hebrew here reads 'Heylel ben yalal shachar' or Helel, son of the (Canaanite) god Shahar, and is a reference to Nebuchanezzar rather than to Satan. The verse in Revelations refers to Jesus as being as bright as venus in the early sky.
The confusion began because the early translator of the Vulgate (Latin translation of the Bible) translated the verse in Isaiah thusly "...12 quomodo cecidisti de
caelo lucifer qui mane oriebaris corruisti in terram qui vulnerabas gentes..." All that the underlined means is 'heavenly light' but Jerome translated it as a name 'Lucifer' and the rest is history.