"I missed" as in "I was absent":
* "Nie byłem/byłam" (Formal) - "I was not" (male/female)
* "Nie było mnie" (Neutral) - "I was not there"
"I missed" as in "I didn't see/hear":
* "Nie zauważyłem/zauważyłam" (Formal) - "I didn't notice" (male/female)
* "Nie widziałem/widziałam" (Formal) - "I didn't see" (male/female)
* "Nie słyszałem/słyszałam" (Formal) - "I didn't hear" (male/female)
* "Nie zauważyłem/zauważyłam tego" (Neutral) - "I didn't notice that"
* "Nie widziałem/widziałam tego" (Neutral) - "I didn't see that"
* "Nie słyszałem/słyszałam tego" (Neutral) - "I didn't hear that"
"I missed" as in "I regret missing":
* "Żałuję, że przegapiłem/przegapiłam" (Formal) - "I regret that I missed" (male/female)
* "Szkoda, że przegapiłem/przegapiłam" (Neutral) - "It's a pity that I missed" (male/female)
"I missed you" as in "I was longing for you":
* "Za Tobą tęskniłem/tęskniłam" (Formal) - "I missed you" (male/female)
* "Tęskniłem/tęskniłam za Tobą" (Neutral) - "I missed you" (male/female)
The best translation will depend on the specific situation you are referring to.