The word fallecimos is the preterite form of fallecer in the first person plural.
See the full fallecer conjugation

fallecer

Nosotros hemos perdonado los tiempos en los que nos han olvidado, cuando casi fallecimos por haber caminado a través del tiempo con ustedes.
We are in forgiveness for the time that you had forgotten us, when we almost perished for we have walked through time with you.
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