Complex sentence: The film is about Pandian (Rajinikanth) who wants to avenge the death of his sister's (Jaysudha) husband's (Charan Raj) death, so he joins the murderer's gang and how he takes revenge forms the crux of "Pandian".
Split into simpler sentences: The film is about Pandian (Rajinikanth) who wants to avenge his sister's (Jaysudha) husband's (Charan Raj) death. He joins the murderer's gang, and how he takes revenge forms the crux of "Pandian".