The white horse Devadatta of Kalki Avatar allegorically symbolizes truthfulness that would be practiced by Kalki Avatar. It is riding a wave of 100% truthfulness a mortal amongst us would don the mettle of Kalki Avatar.
Kalki Avatar would not be any different from us except power of truth exercised by him. Furthermore Kalki Avatar would display resilience, patience, persistence and perseverance of the highest order that can be imagined.
Kalki avatar would possess 100% faith in existence of God and also his system, world of souls’ atmans. A true lover of mankind Kalki Avatar would prove himself the biggest benefactor of humanity. None world over would equalize even part of his power.
The ruthlessness practiced by Kalki Avatar would be without mercy. As detailed by Lord Krishna in Bhagavad Gita the time for practicing forgiveness and mercy is now passé! It is time for Kalki Avatar to react and he would come down heavily on those who spread evil all the time.
Power of truth coupled with firm action makes one an avatar and Kalki is one of them.
Truth primarily symbolizes Dharma and we could also say truth is God personified. Only a true practitioner of truth understands the power 100% truth holds. Kalki avatar would prove nemesis for those following untruthful practices.