とことん

Etymology: Possibly derived from the sound of footsteps going on endlessly (とことこ), with intensification.

Nuance: Implies determination and persistence. Can be:

• Positive: thorough effort, dedication
• Negative: being pushed to extremes, cornered

Common collocations

• とことん話(はな)し合(あ)う (discuss thoroughly)
• とことん追(お)い詰(つ)める (corner completely)
• とことんこだわる (be particular about to the extreme)
• とことんやる (do thoroughly)
• とことん付(つ)き合(あ)う (see it through together)

Similar words

• 徹底的(てっていてき)に (thoroughly) - more formal
• 最後(さいご)まで (until the end) - neutral
• とことんまで (to the very limit) - intensified form

Register: Slightly casual, conversational. More colloquial than 徹底的(てっていてき)に.