This is the 13101st most frequent Polish word.
odwetowych
"Odwetowych" means "retaliatory" in English.
"odwetowe" here acts as an adjective describing the nature of the actions ("działania"), indicating that they were taken in retaliation.
Wojska podjęły działania odwetowe po ataku na ich bazę.
The troops undertook retaliatory actions after the attack on their base.
In this sentence, "odwetowych" is used as an adjective describing "środkach" (measures), again denoting that these measures are retaliatory.
Decyzje o środkach odwetowych muszą być starannie rozważone.
Decisions about retaliatory measures must be carefully considered.
Here, "odwetowa" is an adjective that describes "polityka" (policy), referring to a policy characterized by retaliation.