kesshin
決心
kettei
決定
ketsui
決意
ketsudan
決断
first letter ketsu
決means decision.
so you would better to choose in meaning of second letter.
(or look and feel
)
心center core/heart/the inner man/manas/mind/spirit
定set/settle/come to
意will/volition/purposefulness/animus/idea/intent/meaning/message/plan/signal/thought/design/contemplation/bulesis
断cut out/sever/break