Processes can ignore both SIGTERM and SIGINT, either by choice or because they are stopped or somehow "stuck". In these cases it may be necessary to use the big hammer, the SIGKILL signal. A process cannot ignore SIGKILL:

$ kill 16224
$ jobs -l
[2]+ 16224 Stopped (signal)        xeyes -center blue
$ kill -s SIGKILL
$ jobs -l
[2]+ 16224 Interrupt               xeyes -center blue