const regex = /(?:.*\n){1} End Object/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?:.*\\n){1} End Object', 'gm')
const str = `class a_u000_a extends Emitter; // 이상상태 (독)
defaultproperties
{
Begin Object Class=SpriteEmitter Name=SpriteEmitter1
Acceleration=(Z=-100.000000)
UseColorScale=True
ColorScale(0)=(Color=(B=140,G=64,R=135,A=255))
ColorScale(1)=(RelativeTime=1.000000,Color=(B=120,G=63,R=106,A=255))
ColorMultiplierRange=(X=(Min=0.800000),Y=(Min=0.800000),Z=(Min=0.800000))
FadeOutStartTime=1.080000
FadeOut=True
FadeInEndTime=0.120000
FadeIn=True
MaxParticles=20
RespawnDeadParticles=False
Name="Poison"
StartLocationOffset=(Z=-3.000000)
StartLocationRange=(X=(Min=-8.000000,Max=8.000000),Y=(Min=-8.000000,Max=8.000000))
SpinParticles=True
SpinsPerSecondRange=(X=(Min=0.050000,Max=0.200000))
StartSpinRange=(X=(Max=1.000000))
UseSizeScale=True
UseRegularSizeScale=False
UniformSize=True
SizeScale(0)=(RelativeTime=0.100000,RelativeSize=3.000000)
SizeScale(1)=(RelativeTime=0.360000,RelativeSize=4.600000)
SizeScale(2)=(RelativeTime=1.000000,RelativeSize=6.000000)
StartSizeRange=(X=(Min=2.000000,Max=4.500000),Y=(Min=2.000000,Max=4.500000),Z=(Min=2.000000,Max=4.500000))
InitialParticlesPerSecond=30.000000
AutomaticInitialSpawning=False
DrawStyle=PTDS_AlphaBlend
Texture=Texture'LineageEffectsTextures.Particles.fx_m_t0089'
TextureUSubdivisions=2
TextureVSubdivisions=2
BlendBetweenSubdivisions=True
SubdivisionEnd=4
LifetimeRange=(Min=1.000000,Max=2.000000)
StartVelocityRange=(X=(Min=-80.000000,Max=80.000000),Y=(Min=-80.000000,Max=80.000000),Z=(Min=30.000000,Max=30.000000))
VelocityLossRange=(X=(Min=4.000000,Max=4.000000),Y=(Min=4.000000,Max=4.000000),Z=(Min=4.000000,Max=4.000000))
Name="SpriteEmitter1"
End Object
Emitters(0)=SpriteEmitter'LineageEffect.a_u000_a.SpriteEmitter1'
bNoDelete=False
DrawScale=0.200000
}`;
const subst = ` End Object`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions