Kyoushoku Soukou Guyver (2005), Kakugo no Susume Recommendations
In both anime, the main protagonist has access to an armor that gives them superhuman powers to the user and enables them to battle various monster opponents. Both are dark sci-fi action-packed anime that contains a lot of blood and gore. Differences between the two is that they have different settings (Apocalypse Zero is set in a post-apocalyptic world while The Guyver is not) and Apocalypse Zero is more wacky and over the top compare to The Guyver. The Guyver also has a better story and is more serious compare to Apocalypse Zero. If you enjoy one, you should like the other as well.