Is it safe to sell used Android phone (re. personal data) ?

Phone's screen broke, was able to unlock / backup / wipe data remotely via Samsung's SmartThings / Google Find My Mobile.

Made sure phone was charged, after data wipe alarms stopped ringing, smart watch stopped seeing it ... shall I assume all data was wiped successfully (no screen to turn on and check) ?

My concern is that it was unlocked and someone who buys it can fix the screen and get access to my personal data ...