Lahore Kebab House on 2-10 umberston street does pakistani food that will destroy you - ask for 'extra hot' karahi and they'll look genuinely concerned before bringing something requiring multiple lassis.

For thai: som saa on commercial street jungle curry is properly fiery. The sri lankan places around elephant & castle serve genuinely punishing spice levels. Look for places like hot stuff on wilcox road that don't mess around with heat.

Dishoom's black daal is mild instagram food compared to proper brick lane curry houses between numbers 90-110.