its hard to make knight crit very high.
the most important things would be fearles+2x glor bellos, elite sword +1 with high damage and crit, much slots full of ahstals. as much ashtals in ur stuff as possible, like in boots, pants. use only might lvl 6 in cap, neck, rings (if u have enough ressistance).
and ur lvl is very important u must be 120 if u want to make high crits, even its hard to lvl with knight. gl making a tank.