If you deleted files, and don't know what you deleted (and didn't back anything up), its very hard for anyone to help you.
You said stock phone, but I assume you are rooted, as altering system files is not possible otherwise. Do you have custom recovery installed (TWRP or CWM)? If so, find the appropriate nandroid from the nandroid collection and rstore it. Or find a stock rooted or stock-ish custom ROM and flash it.
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Phone: AT&T HTC One (M8)
Tablet: Samsung Galaxy Tab Pro 8.4 (WiFi only)