extenuate, palliate, qualify, alleviate, allay, attenuate, obtund, remitigate, lenify, abate, more...

aggravate, exacerbate, worsen

reduce, alleviate, ameliorate, redress, mitigation, mitigative, mitigatory, more...

make less severe,   make safer,   reduce risk,   lessen the impact,   to make less severe,   make less harsh,   make less dangerous,   make milder,   reduce the impact,   reduce the risk