There is no definitive answer, because rat behavior depends on several factors.
Rats are social animals: They live in colonies with complex social structures and often show care for young or injured members.
Competition for resources: In crowded environments or when food, water, or shelter is limited, an injured rat might be seen as a threat by healthier rats.
Individual personalities: Like humans, rats have distinct temperaments. Some are compassionate and protective, while others are more aggressive.
General Scenarios
Colony member: If the injured rat is part of the same colony, other rats are more likely to show compassion, possibly helping it find food or offering protection.
Stranger: If the injured rat is unfamiliar, the other rat may avoid it or even attack it.
Important Factors
Severity of injury: A severely injured rat may be perceived as a threat and attacked.
Age and sex: Young rats and females tend to be more compassionate.
Availability of resources: When food and shelter are plentiful, aggression is less likely.
Ultimately, it is impossible to know for sure whether a rat will hurt an injured one without observing the specific situation.