LG Optimus Big LU6800 Android hard resetTry this key combo
WARNING: All of your data will be lost!
Use Hard Reset (Factory Reset) to initialise your phone.
When the phone is turned off, press and hold the Power + Volume down keys at the same time (for over ten seconds), the phone will turn on and perform factory reset immediately.
Please note, after you perform Hard Reset, all your data and applications on your phone will be erased. This cannot be reversed.
You can check it in korean manual
Pls leave comment if this is not correct.
LU6800 Battery reset
If your Android smartphone is frozen just pull out battery, wait for a few seconds and reindert it.
You can use LG Mobile Support tool to repair some LG cell phone model, after download select menu Customer Support > Recovery Phone
If you know LG Optimus Big LU6800 Android hard reset with buttons / keys pls leave comment.