Are they scary ...

Without a divorce in wedlock he is cheating and lying with another woman,

she lying with him who is in wedlock,

for are they scary??

no they arent 

they are craving cruel wicked who can cheat for their mean desires of pleasure. 

for they call declare themselves God, do they really represent him?

God has born given an example how to lead a human life, Ram, Krishna, and Kalki(who hasnt born yet).

You have to follow dharma which is good and if you cheat and becoming wicked how can you say so, instead you are a evil who doesnt follow dharma which is good and never you hold that power. 

Yes Lord shiva gives boon to rakshas and kills them ruthlessly for their bad deeds. 

one who kills others life for sure they are evil and there is only 1/4 quarter time to stamp on God, in this kali yuga, the last padam of dharma of God, for they are in return going to be killed in hands of God only. 

Here she ebode and follower of Dharma, can evil stamp on her but cannot kill her the dharma never dies its eternal it only vacates body,,,, 

Dharmo Rakshathi Rakshithiha Adharmasya vinashanaya. 

This is from Vedas. Nobody can change it is the Parama Sathyaha.