staunch

a very loyal and committed supporter

a very loyal and reliable ally

a firm and dedicated supporter of a cause or person

a very firm and determined opponent

someone with very strong conservative political views

a very strong and resolute defence

someone with a very strong and unwavering belief

someone with very strong socialist political views

a very firm and unwavering refusal

to stop or slow down the flow of blood from a wound

to stop or slow down the movement of a liquid