But Catholics of the British-province love him and his party on Friday won 24 seats, ahead of the 18 seats won by his more moderate rivals in the SDLP.
Charismatic, tough and articulate, Adams has been a central figure in shaping Northern Ireland's recent history, notably through his efforts in persuading the IRA to make unprecedented moves over disarmament.
Protestants see Adams, 55, as the brazen face of IRA extremism, but for many Catholics he is a champion unafraid to stand up for their rights.
Whatever his image, his role in persuading the IRA to renounce its armed struggle has turned him from a pariah figure in London to one who last month attended talks inside 10 Downing Street – a building the IRA attacked with mortars in 1991.
Adams has headed Sinn Fein for two decades.
In 1971, he was detained without trial and then arrested again in 1973 on suspicion of running the IRA's Belfast Brigade.
After attempting escape, Adams was sentenced to 18 months in prison and in February 1978 he was charged with membership of the IRA but was freed because of insufficient evidence.
Since then, Adam's supporters say, he has embarked on a brave attempt to wean the republican movement away from its belief in violence as the means of achieving its political ends.
Adams was elected member of the British parliament in 1983, lost the seat in 1992 and was then re-elected but refused to attend parliament because he would not swear the required oath of allegiance to the British Queen.