Vengeance is a full 36-level megawad for Ultimate Doom by Paul Fleschute. With some exceptions, each level is similar in style to the original it replaces, but larger and more detailed. The WAD uses textures from various other projects for a grittier look, as well as music by David Shaw and Mark Klem. Released on March 11, 1999, Vengeance is an improved version of the author's earlier work PSFDOOM. Some of the added levels were contributed by Fleschute's brother.
- E1M5 starts with the same room as original E1M5 but then is totally different. E1M6 follows a similar pattern.
- Some levels are modified levels that appeared in the author's earlier megawad Invasion. E1M7, E2M3, and E4M7 are among them.
- Additionally, E4M1, E4M2, and E4M7 are largely based on levels in another episode by Fleschute, Episode Hell.
- E4M8 is the biggest and final level in the game. It is mostly new, but embeds the design of E4M8 of Episode Hell within it.
- The secret level E4M9 is a remake of Quake's E1M2.