Soldner-X: Himmelssturmer

This trophy is another grind. As you shoot enemies, you’ll build up chains. The chain meter is in the bottom right of the screen. When the bar turns green, change your weapons with R1. Don’t worry about this trophy as much since it’ll come eventually.

An easy way to grind this out is below.

A good level to get chains is level 3 (the one with space debris), just replay it over and over in training mode.

As SuperNova69 explained, switch weapon (or switch forth and back to ur current) with the L1/R1 buttons (default control). Make sure to do it as soon as the chain gauge bar in the lower-right turns green to increase your chain counter, and make sure that the gauge doesn't fill completely (will be fully green, fading into red at the end) because this will reset the gauge (same effect as changing weapon when the gauge is blue).

Credit to RyujiSakujo for this info.