 If you liked
GetBackers
|
 ...then you might like
Samurai Deeper Kyou
|
These two series can be considered "brother" series. They were both serialized around the same time, both ended around the same time and therefore had nearly the same number of volumes. Both series have similar artwork and deal with a group of strong fighters with unique abilities dealing with the nightmares of their past. Getbackers is slightly less serious than SDK.
The settings of these two manga are completely different and the moods are a little different but otherwise they are quite similar. They both have interesting characters with unique abilities and mysterious backstories that have banded together, friends turned enemies, awesome battles, and near the end they fight against powerful opponent(s) to change their world.