i can describe what i remember

i think the main character's name starts with 't'

he has this special mark that appears on his forehead, and whenever it happens he gets tremendous power

there is one enemy who i think is an alligator? (i forgot) in a castle or something

2nd to last episode he fights his dad who also has the same mark that appears on his forehead and gets tremendous power

2nd to last episode he is beaten by his dad and is about to die under water, but he comes back with that mark and fights him in the next episode


sry if its vague, but it's a really old anime, i watched it when i was elementary school in korea, which was about 15+ years ago

totoro

it's not totoro lol... it's a person not an animal

Tenchi

just looked this up and it's not it sadly

zatch bell? lol no clue

taiga?

the setting is not in modern, aka there's castles and stuff

castles....
Kanojo ga Flag wo Oraretara

just looked and it's not this

the one i remember is not ecchi

it's not hantei either

there is hardly any tlts or anything like that

not school girl either, or school life

it's more of an action, a young boy who goes around fighting foes, and when he gets this mark on his forehead, he gets extra power