Using:
Account ID : accountname
Character ID #1 : character1
Character ID #2 : character2
Character ID #3 : character3
Code:
delete from tb_user where straccountid = 'accountname'
delete from account_char where straccountid = 'accountname'
delete from account_nation_check where straccountid = 'accountname'
update battle set strusername = 'NULL' where strusername = 'character1'
update battle set strusername = 'NULL' where strusername = 'character2'
update battle set strusername = 'NULL' where strusername = 'character3'
delete from currentuser where straccountid = 'accountname'
delete from friend_list where struserid = 'character1'
delete from friend_list where struserid = 'character2'
delete from friend_list where struserid = 'character3'
update hero_user set struserid = 'NULL' where struserid = 'character1'
update hero_user set struserid = 'NULL' where struserid = 'character2'
update hero_user set struserid = 'NULL' where struserid = 'character3'
update king_system set strkingname = 'NULL' where strkingname = 'character1'
update king_system set strkingname = 'NULL' where strkingname = 'character2'
update king_system set strkingname = 'NULL' where strkingname = 'character3'
delete from king_ballot_box where straccountid = 'accountname'
update king_candidacy_notice_board set struserid = 'NULL' where struserid = 'character1'
update king_candidacy_notice_board set struserid = 'NULL' where struserid = 'character2'
update king_candidacy_notice_board set struserid = 'NULL' where struserid = 'character3'
update king_election_list set strname = 'NULL' where strname = 'Character1'
update king_election_list set strname = 'NULL' where strname = 'Character2'
update king_election_list set strname = 'NULL' where strname = 'Character3'
delete from knights where chief = 'character1'
delete from knights where chief = 'character2'
delete from knights where chief = 'character3'
update knights set vicechief_1 = 'NULL' where vicechief_1 = 'Character1'
update knights set vicechief_1 = 'NULL' where vicechief_1 = 'Character2'
update knights set vicechief_1 = 'NULL' where vicechief_1 = 'Character3'
update knights set vicechief_2 = 'NULL' where vicechief_2 = 'Character1'
update knights set vicechief_2 = 'NULL' where vicechief_2 = 'Character2'
update knights set vicechief_2 = 'NULL' where vicechief_2 = 'Character3'
update knights set vicechief_3 = 'NULL' where vicechief_3 = 'Character1'
update knights set vicechief_3 = 'NULL' where vicechief_3 = 'Character2'
update knights set vicechief_3 = 'NULL' where vicechief_3 = 'Character3'
delete from knights_user where struserid = 'character1'
delete from knights_user where struserid = 'character2'
delete from knights_user where struserid = 'character3'
update user_knights_rank set strelmouserid = 'NULL', strelmoknightsname = 'NULL' where strelmouserid = 'CHARACTER1'
update user_knights_rank set strelmouserid = 'NULL', strelmoknightsname = 'NULL' where strelmouserid = 'CHARACTER2'
update user_knights_rank set strelmouserid = 'NULL', strelmoknightsname = 'NULL' where strelmouserid = 'CHARACTER3'
update user_knights_rank set strkarususerid = 'NULL', strkarusknightsname = 'NULL' where strelmouserid = 'CHARACTER1'
update user_knights_rank set strkarususerid = 'NULL', strkarusknightsname = 'NULL' where strelmouserid = 'CHARACTER2'
update user_knights_rank set strkarususerid = 'NULL', strkarusknightsname = 'NULL' where strelmouserid = 'CHARACTER3'
delete from userdata where struserid = 'character1'
delete from userdata where struserid = 'character2'
delete from userdata where struserid = 'character3'
delete from warehouse where straccountid = 'accountname'
P.S. Didn't do all of it, just the relevant ones.
Actually, I just got lazy.