There are several examples of characters with particularly extensive cybernetic modification, though none that I would consider notably close in design to Darth Vader in canon continuity.
General Grievous was a cyborg who had such extensive modification that his organic parts consisted of little more than a brain, eyes and a few internal organs.
Mercenaries from the Guavian Death Gang that confronted Han Solo during the events of The Force Awakens were cybernetically enhanced with artificial organs and armor similar to Vader's, though they were the result of voluntary augmentation rather than necessitated by injury.
Saw Gerrera had a cybernetic leg and a pressure suit to support his damaged lungs.
From the Legends continuity there are several other examples, many of which bear a significant resemblance to Vader's cybernetics. Other characters with armored life support systems include Lumiya, another dark Jedi who received cybernetic prostheses explicitly modeled after Vader's, Azlyn Rae, a force user who was forced against her will to wear a set of life-preserving armor after being mortally wounded, Hogrum Chalk, an armorer who created Azlyn Rae's suit and had similar life-saving cybernetics, and Vader's secret apprentice Galen Marek in the non-canon dark side ending of the game Star Wars: The Force Unleashed, who wore cybernetic Sith Stalker Armor.
Face masks to help damaged respiratory systems also seemed to be extremely popular among dark lords of the Sith in the Legends continuity, as Darth Malgus, Darth Plagueis, and Darth Tenebrous all had some variety of cybernetic respirators, and Darth Malak had a prosthetic lower jaw.
