Neki aur badi hai Mangal do bhai, jahan das mein insaaf ki talwar hua, wahi chaar mein bhai ki peeth pe chhuri chalai.
Goodness and evil are the two brothers of Mars; where in the 10th it became the sword of justice, there in the 4th it stabbed a knife in the brother's back.
Mars (Mangal) has two distinct forms in Lal Kitab: "Mangal Nek" (Positive Mars) and "Mangal Bad" (Negative Mars).
When Mars sits in the 10th house, it is exalted (Uchha). Here, Mars becomes the ultimate protector. It is the "Sword of Justice" ("insaaf ki talwar"). The person will fight for the weak, uphold the law, and protect their family with honor.
But when Mars sits in the 4th house, it becomes debilitated (Neech). Here, the warrior turns into a coward. Instead of fighting enemies face-to-face, this Mars creates a person who will betray their own family. They will literally "stab a knife in their brother's back" ("bhai ki peeth pe chhuri chalai") over property or petty disputes.