should slacken
Regular verb: slacken - slackened- slackened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I'd slacken
you'd slacken
she'd slacken
we'd slacken
you'd slacken
they'd slacken 	I'd be slackening
you'd be slackening
she'd be slackening
we'd be slackening
you'd be slackening
they'd be slackening	I should've slackened
you should've slackened
she should've slackened
we should've slackened
you should've slackened
they should've slackened	I should've been slackening
you should've been slackening
she should've been slackening
we should've been slackening
you should've been slackening
they should've been slackening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I shouldn't slacken
you shouldn't slacken
she shouldn't slacken
we shouldn't slacken
you shouldn't slacken
they shouldn't slacken 	I shouldn't be slackening
you shouldn't be slackening
she shouldn't be slackening
we shouldn't be slackening
you shouldn't be slackening
they shouldn't be slackening	I shouldn't have slackened
you shouldn't have slackened
she shouldn't have slackened
we shouldn't have slackened
you shouldn't have slackened
they shouldn't have slackened	I shouldn't have been slackening
you shouldn't have been slackening
she shouldn't have been slackening
we shouldn't have been slackening
you shouldn't have been slackening
they shouldn't have been slackening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
should I slacken?
should you slacken?
should she slacken?
should we slacken?
should you slacken?
should they slacken? 	should I be slackening?
should you be slackening?
should she be slackening?
should we be slackening?
should you be slackening?
should they be slackening? 	should I have slackened?
should you have slackened?
should she have slackened?
should we have slackened?
should you have slackened?
should they have slackened? 	should I have been slackening?
should you have been slackening?
should she have been slackening?
should we have been slackening?
should you have been slackening?
should they have been slackening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
shouldn't I slacken?
shouldn't you slacken?
shouldn't she slacken?
shouldn't we slacken?
shouldn't you slacken?
shouldn't they slacken? 	shouldn't I be slackening?
shouldn't you be slackening?
shouldn't she be slackening?
shouldn't we be slackening?
shouldn't you be slackening?
shouldn't they be slackening? 	shouldn't I have slackened?
shouldn't you have slackened?
shouldn't she have slackened?
shouldn't we have slackened?
shouldn't you have slackened?
shouldn't they have slackened? 	shouldn't I have been slackening?
shouldn't you have been slackening?
shouldn't she have been slackening?
shouldn't we have been slackening?
shouldn't you have been slackening?
shouldn't they have been slackening?