Open the Phone app
Tap Contacts
Find and tap the contact you want to delete
Tap Edit
Scroll down and tap Delete Contact
Confirm by tapping Delete Contact again
Open the Settings app
Tap Contacts
Tap Accounts
Select the account that contains the contact
Turn off Contacts sync for that account (optional)
Return to Contacts and delete the contact as needed
Open the Contacts app
Find and tap the contact
Tap Edit
Tap Delete Contact
Confirm by tapping Delete Contact again
If the contact is synced from iCloud/Google/another account, delete it from that account’s contacts page instead (then refresh on iPhone)