All of the terms are clear.

Tankie is a derogatory term used to left-punch against those who support socialist countries that opposed US+EU hegemony and colonialism.

Leftist is a generic word to talk about everyone who considers themselves progressive and wants things like a welfare state, but it's a relatively umbrella term that includes or not socialdemocrats (pro-capitalist reformists) depending on who you ask.

Liberal, in the English language and due to US influence, is generally used in a derogatory way to refer to western progressives who believe capitalism can be stewarded and reformed into social justice. In the rest of the world it's a word more often used to refer to people who believe capitalism is best left untouched and it will take care of itself.